diff --git a/extra/L-system/L-system.factor b/extra/L-system/L-system.factor
new file mode 100644
index 0000000000..97a971de47
--- /dev/null
+++ b/extra/L-system/L-system.factor
@@ -0,0 +1,448 @@
+
+USING: accessors arrays assocs colors combinators.short-circuit
+kernel locals math math.functions math.matrices math.order
+math.parser math.trig math.vectors opengl opengl.demo-support
+opengl.gl sbufs sequences strings ui.gadgets ui.gadgets.worlds
+ui.gestures ui.render ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+IN: L-system
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+TUPLE: <turtle> pos ori angle length thickness color vertices saved ;
+
+DEFER: default-L-parser-values
+
+: reset-turtle ( turtle -- turtle )
+  { 0 0 0 } clone   >>pos
+  3 identity-matrix >>ori
+  V{ } clone >>vertices
+  V{ } clone >>saved
+
+  default-L-parser-values ;
+
+: turtle ( -- turtle ) <turtle> new reset-turtle ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+:: step-turtle ( TURTLE LENGTH -- turtle )
+
+  TURTLE
+    TURTLE pos>>   TURTLE ori>> { 0 0 LENGTH } m.v   v+
+  >>pos ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+:: Rx ( ANGLE -- Rx )
+  
+  [let | ANGLE [ ANGLE deg>rad ] |
+
+    [let | A [ ANGLE cos     ]
+           B [ ANGLE sin neg ]
+           C [ ANGLE sin     ]
+           D [ ANGLE cos     ] |
+
+      { { 1 0 0 }
+        { 0 A B }
+        { 0 C D } }
+
+    ] ] ;
+
+:: Ry ( ANGLE -- Ry )
+  
+  [let | ANGLE [ ANGLE deg>rad ] |
+
+    [let | A [ ANGLE cos     ]
+           B [ ANGLE sin     ]
+           C [ ANGLE sin neg ]
+           D [ ANGLE cos     ] |
+
+      { { A 0 B }
+        { 0 1 0 }
+        { C 0 D } }
+
+    ] ] ;
+
+:: Rz ( ANGLE -- Rz )
+  
+  [let | ANGLE [ ANGLE deg>rad ] |
+
+    [let | A [ ANGLE cos     ]
+           B [ ANGLE sin neg ]
+           C [ ANGLE sin     ]
+           D [ ANGLE cos     ] |
+
+      { { A B 0 }
+        { C D 0 }
+        { 0 0 1 } }
+
+    ] ] ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+:: apply-rotation ( TURTLE ROTATION -- turtle )
+  
+  TURTLE  TURTLE ori>> ROTATION m.  >>ori ;
+
+: rotate-x ( turtle angle -- turtle ) Rx apply-rotation ;
+: rotate-y ( turtle angle -- turtle ) Ry apply-rotation ;
+: rotate-z ( turtle angle -- turtle ) Rz apply-rotation ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: pitch-up   ( turtle angle -- turtle ) neg rotate-x ;
+: pitch-down ( turtle angle -- turtle )     rotate-x ;
+
+: turn-left  ( turtle angle -- turtle )     rotate-y ;
+: turn-right ( turtle angle -- turtle ) neg rotate-y ;
+
+: roll-left  ( turtle angle -- turtle ) neg rotate-z ;
+: roll-right ( turtle angle -- turtle )     rotate-z ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: V ( -- V ) { 0 1 0 } ;
+
+: X ( turtle -- 3array ) ori>> [ first  ] map ;
+: Y ( turtle -- 3array ) ori>> [ second ] map ;
+: Z ( turtle -- 3array ) ori>> [ third  ] map ;
+
+: set-X ( turtle seq -- turtle ) over ori>> [ set-first  ] 2each ;
+: set-Y ( turtle seq -- turtle ) over ori>> [ set-second ] 2each ;
+: set-Z ( turtle seq -- turtle ) over ori>> [ set-third  ] 2each ;
+
+:: roll-until-horizontal ( TURTLE -- turtle )
+
+  TURTLE
+  
+    V         TURTLE Z  cross normalize  set-X
+
+    TURTLE Z  TURTLE X  cross normalize  set-Y ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+:: strafe-up ( TURTLE LENGTH -- turtle )
+  TURTLE 90 pitch-up LENGTH step-turtle 90 pitch-down ;
+
+:: strafe-down ( TURTLE LENGTH -- turtle )
+  TURTLE 90 pitch-down LENGTH step-turtle 90 pitch-up ;
+
+:: strafe-left ( TURTLE LENGTH -- turtle )
+  TURTLE 90 turn-left LENGTH step-turtle 90 turn-right ;
+
+:: strafe-right ( TURTLE LENGTH -- turtle )
+  TURTLE 90 turn-right LENGTH step-turtle 90 turn-left ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: polygon ( vertices -- ) GL_POLYGON glBegin [ first3 glVertex3d ] each glEnd ;
+
+: start-polygon ( turtle -- turtle ) dup vertices>> delete-all ;
+
+: finish-polygon ( turtle -- turtle ) dup vertices>> polygon ;
+
+: polygon-vertex ( turtle -- turtle ) dup [ pos>> ] [ vertices>> ] bi push ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: record-vertex ( turtle -- turtle ) dup pos>> first3 glVertex3d ;
+
+: draw-forward ( turtle length -- turtle )
+  GL_LINES glBegin [ record-vertex ] dip step-turtle record-vertex glEnd ;
+
+: move-forward ( turtle length -- turtle ) step-turtle polygon-vertex ;
+
+: sneak-forward ( turtle length -- turtle ) step-turtle ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: scale-length ( turtle m -- turtle ) over length>> * >>length ;
+: scale-angle  ( turtle m -- turtle ) over angle>>  * >>angle  ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: set-thickness ( turtle i -- turtle ) dup glLineWidth >>thickness ;
+
+: scale-thickness ( turtle m -- turtle )
+  over thickness>> * 0.5 max set-thickness ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: color-table ( -- colors )
+  {
+    T{ rgba f 0    0    0    1 } ! black
+    T{ rgba f 0.5  0.5  0.5  1 } ! grey
+    T{ rgba f 1    0    0    1 } ! red
+    T{ rgba f 1    1    0    1 } ! yellow
+    T{ rgba f 0    1    0    1 } ! green
+    T{ rgba f 0.25 0.88 0.82 1 } ! turquoise
+    T{ rgba f 0    0    1    1 } ! blue
+    T{ rgba f 0.63 0.13 0.94 1 } ! purple
+    T{ rgba f 0.00 0.50 0.00 1 } ! dark green
+    T{ rgba f 0.00 0.82 0.82 1 } ! dark turquoise
+    T{ rgba f 0.00 0.00 0.50 1 } ! dark blue
+    T{ rgba f 0.58 0.00 0.82 1 } ! dark purple
+    T{ rgba f 0.50 0.00 0.00 1 } ! dark red
+    T{ rgba f 0.25 0.25 0.25 1 } ! dark grey
+    T{ rgba f 0.75 0.75 0.75 1 } ! medium grey
+    T{ rgba f 1    1    1    1 } ! white
+  } ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+! : material-color ( color -- )
+!   GL_FRONT_AND_BACK GL_AMBIENT_AND_DIFFUSE rot gl-material ;
+
+: material-color ( color -- )
+  GL_FRONT_AND_BACK GL_AMBIENT_AND_DIFFUSE rot color>raw 4array gl-material ;
+
+: set-color ( turtle i -- turtle )
+  dup color-table nth dup gl-color material-color >>color ;
+
+: inc-color ( turtle -- turtle ) dup color>> 1 + set-color ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: save-turtle    ( turtle -- turtle ) dup clone over saved>> push ;
+: restore-turtle ( turtle -- turtle )                saved>> pop  ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: default-L-parser-values ( turtle -- turtle )
+  1 >>length 45 >>angle 1 >>thickness 2 >>color ;
+
+: L-parser-dialect ( -- commands )
+
+  {
+      { "+" [ dup angle>> turn-left  ] }
+      { "-" [ dup angle>> turn-right ] }
+      { "&" [ dup angle>> pitch-down ] }
+      { "^" [ dup angle>> pitch-up   ] }
+      { "<" [ dup angle>> roll-left  ] }
+      { ">" [ dup angle>> roll-right ] }
+
+      { "|" [ 180.0         rotate-y ] }
+      { "%" [ 180.0         rotate-z ] }
+      { "$" [ roll-until-horizontal  ]  }
+
+      { "F" [ dup length>>     draw-forward  ] }
+      { "Z" [ dup length>> 2 / draw-forward  ] }
+      { "f" [ dup length>>     move-forward  ] }
+      { "z" [ dup length>> 2 / move-forward  ] }
+      { "g" [ dup length>>     sneak-forward ] }
+      { "." [ polygon-vertex                 ] }
+
+      { "[" [ save-turtle      ] }
+      { "]" [ restore-turtle   ] }
+      
+      { "{" [ start-polygon    ] }
+      { "}" [ finish-polygon   ] }
+
+      { "/" [ 1.1 scale-length    ] } ! double quote command in lparser
+      { "'" [ 0.9 scale-length    ] }
+      { ";" [ 1.1 scale-angle     ] }
+      { ":" [ 0.9 scale-angle     ] }
+      { "?" [ 1.4 scale-thickness ] }
+      { "!" [ 0.7 scale-thickness ] }
+
+      { "c" [ dup color>> 1 + color-table length mod set-color ] }
+
+    }
+    ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+TUPLE: <L-system> < gadget
+  camera display-list
+  commands axiom rules string ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: open-paren  ( -- ch ) CHAR: ( ;
+: close-paren ( -- ch ) CHAR: ) ;
+
+: open-paren?  ( obj -- ? ) open-paren  = ;
+: close-paren? ( obj -- ? ) close-paren = ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+:: read-instruction ( STRING -- next rest )
+  
+  { [ STRING length 1 > ] [ STRING second open-paren? ] } 0&&
+    [ STRING  close-paren STRING index 1 + cut ]
+    [ STRING  1                            cut ]
+  if ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+:: iterate-string-loop ( STRING RULES ACCUM -- )
+  STRING empty? not
+    [
+      STRING read-instruction
+    
+      [let | REST [ ] NEXT [ ] |
+
+        NEXT 1 head RULES at  NEXT  or  ACCUM push-all
+
+        REST RULES ACCUM iterate-string-loop ]
+    ]
+  when ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+:: iterate-string ( STRING RULES -- string )
+
+  [let | ACCUM [ STRING length  10 *  <sbuf> ] |
+
+    STRING RULES ACCUM iterate-string-loop
+
+    ACCUM >string ] ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+:: interpret-string ( STRING COMMANDS -- )
+
+  STRING empty? not
+    [
+      STRING read-instruction
+
+      [let | REST [ ] NEXT [ ] |
+
+        [let | COMMAND [ NEXT 1 head COMMANDS at ] |
+
+          COMMAND
+            [
+              NEXT length 1 =
+                [ COMMAND call ]
+                [
+                  NEXT 2 tail 1 head* string>number
+                  COMMAND 1 tail*
+                  call
+                ]
+              if
+            ]
+          when ]
+
+        REST COMMANDS interpret-string ]
+    ]
+  when ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+:: iterate-L-system-string ( L-SYSTEM -- )
+  L-SYSTEM string>>
+  L-SYSTEM rules>>
+  iterate-string
+  L-SYSTEM (>>string) ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+:: do-camera-look-at ( CAMERA -- )
+
+  [let | EYE   [ CAMERA pos>> ]
+         FOCUS [ CAMERA clone 1 step-turtle pos>> ]
+         UP    [ CAMERA clone 90 pitch-up 1 step-turtle pos>> CAMERA pos>> v- ]
+       |
+
+    EYE FOCUS UP gl-look-at ] ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+:: generate-display-list ( L-SYSTEM -- )
+
+  L-SYSTEM find-gl-context
+
+  L-SYSTEM display-list>> GL_COMPILE glNewList
+
+    turtle
+    L-SYSTEM string>>
+    L-SYSTEM commands>>
+    interpret-string
+    drop
+
+  glEndList ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+M:: <L-system> draw-gadget* ( L-SYSTEM -- )
+
+  black gl-clear
+
+  GL_FLAT glShadeModel
+
+  GL_PROJECTION glMatrixMode
+  glLoadIdentity
+  -1 1 -1 1 1.5 200 glFrustum
+
+  GL_MODELVIEW glMatrixMode
+
+  glLoadIdentity
+
+  L-SYSTEM camera>> do-camera-look-at
+
+  GL_FRONT_AND_BACK GL_LINE glPolygonMode
+
+  ! draw axis
+  white gl-color GL_LINES glBegin { 0 0 0 } gl-vertex { 0 0 1 } gl-vertex glEnd
+
+  L-SYSTEM display-list>> glCallList ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+M:: <L-system> graft* ( L-SYSTEM -- )
+
+  L-SYSTEM find-gl-context
+
+  1 glGenLists L-SYSTEM (>>display-list) ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+M:: <L-system> pref-dim* ( L-SYSTEM -- dim ) { 400 400 } ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+:: camera-left ( L-SYSTEM -- )
+  L-SYSTEM camera>> 5 turn-left drop
+  L-SYSTEM relayout-1 ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+:: with-camera ( L-SYSTEM QUOT -- )
+  L-SYSTEM camera>> QUOT call drop
+  L-SYSTEM relayout-1 ;
+
+<L-system>
+H{
+  { T{ key-down f f "LEFT"  } [ [  5 turn-left   ] with-camera ] }
+  { T{ key-down f f "RIGHT" } [ [  5 turn-right  ] with-camera ] }
+  { T{ key-down f f "UP"    } [ [  5 pitch-down  ] with-camera ] }
+  { T{ key-down f f "DOWN"  } [ [  5 pitch-up    ] with-camera ] }
+  
+  { T{ key-down f f "a"     } [ [  1 step-turtle ] with-camera ] }
+  { T{ key-down f f "z"     } [ [ -1 step-turtle ] with-camera ] }
+
+  {
+    T{ key-down f f "x" }
+    [
+      dup iterate-L-system-string
+      dup generate-display-list
+      dup relayout-1
+      drop
+    ]
+  }
+    
+}
+set-gestures
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: L-system ( -- L-system )
+
+  <L-system> new-gadget
+  
+    turtle 45 turn-left 45 pitch-up 5 step-turtle 180 turn-left >>camera ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
diff --git a/extra/L-system/models/abop-1/abop-1.factor b/extra/L-system/models/abop-1/abop-1.factor
new file mode 100644
index 0000000000..45cc522470
--- /dev/null
+++ b/extra/L-system/models/abop-1/abop-1.factor
@@ -0,0 +1,29 @@
+
+USING: accessors kernel ui L-system ;
+
+IN: L-system.models.abop-1
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: abop-1 ( <L-system> -- <L-system> )
+  
+  L-parser-dialect >>commands
+
+  "c(12)FFAL" >>axiom
+
+  {
+    { "A" "F[&'(.8)!BL]>(137)'!(.9)A"   }
+    { "B" "F[-'(.8)!(.9)$CL]'!(.9)C"    }
+    { "C" "F[+'(.8)!(.9)$BL]'!(.9)B"    }
+    
+    { "L" "~c(8){+(30)f-(120)f-(120)f}" }
+  }
+  >>rules
+
+  dup axiom>> >>string ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: main ( -- ) [ L-system abop-1 "L-system" open-window ] with-ui ;
+
+MAIN: main
diff --git a/extra/fuel/fuel.factor b/extra/fuel/fuel.factor
index a3cb6a9a22..80d8cde654 100644
--- a/extra/fuel/fuel.factor
+++ b/extra/fuel/fuel.factor
@@ -5,8 +5,8 @@ USING: accessors arrays assocs classes.tuple combinators
 compiler.units continuations debugger definitions help help.crossref
 help.markup help.topics io io.pathnames io.streams.string kernel lexer
 make math math.order memoize namespaces parser prettyprint sequences
-sets sorting source-files strings summary tools.vocabs vectors vocabs
-vocabs.parser words ;
+sets sorting source-files strings summary tools.crossref tools.vocabs
+vectors vocabs vocabs.parser words ;
 
 IN: fuel
 
@@ -58,7 +58,7 @@ GENERIC: fuel-pprint ( obj -- )
 M: object fuel-pprint pprint ; inline
 
 : fuel-maybe-scape ( ch -- seq )
-    dup "?#()[]'`" member? [ CHAR: \ swap 2array ] [ 1array ] if ;
+    dup "\\\"?#()[]'`" member? [ CHAR: \ swap 2array ] [ 1array ] if ;
 
 M: word fuel-pprint
     name>> V{ } clone [ fuel-maybe-scape append ] reduce >string write ;
@@ -151,7 +151,7 @@ SYMBOL: :uses
 : fuel-run-file ( path -- )
     [ fuel-set-use-hook run-file ] curry with-scope ; inline
 
-: fuel-with-autouse ( quot --  )
+: fuel-with-autouse ( ... quot: ( ... -- ... ) -- ... )
     [ auto-use? on fuel-set-use-hook call ] curry with-scope ; inline
 
 : (fuel-get-uses) ( lines -- )
@@ -184,13 +184,16 @@ SYMBOL: :uses
     [ [ first ] dip first <=> ] sort ; inline
 
 : fuel-format-xrefs ( seq -- seq' )
-    [ word? ] filter [ fuel-word>xref ] map fuel-sort-xrefs ;
+    [ word? ] filter [ fuel-word>xref ] map ; inline
 
 : fuel-callers-xref ( word -- )
-    usage fuel-format-xrefs fuel-eval-set-result ; inline
+    usage fuel-format-xrefs fuel-sort-xrefs fuel-eval-set-result ; inline
 
 : fuel-callees-xref ( word -- )
-    uses fuel-format-xrefs fuel-eval-set-result ; inline
+    uses fuel-format-xrefs fuel-sort-xrefs fuel-eval-set-result ; inline
+
+: fuel-apropos-xref ( str -- )
+    words-matching fuel-format-xrefs fuel-eval-set-result ; inline
 
 ! Completion support
 
@@ -289,6 +292,23 @@ MEMO: fuel-find-word ( name -- word/f )
     fuel-find-word [ [ auto-use? on (fuel-word-see) ] with-scope ] [ f ] if*
     fuel-eval-set-result ; inline
 
+: (fuel-vocab-help) ( name -- element )
+    \ article swap dup >vocab-link
+    [
+        [ summary [ , ] [ "No summary available" , ] if* ]
+        [ drop \ $nl , ]
+        [ vocab-help article [ content>> % ] when* ] tri
+    ] { } make 3array ;
+
+: fuel-vocab-help ( name -- )
+    (fuel-vocab-help) fuel-eval-set-result ; inline
+
+: (fuel-index) ( seq -- seq )
+    [ [ >link name>> ] [ article-title ] bi 2array \ $subsection prefix ] map ;
+
+: fuel-index ( quot: ( -- seq ) -- )
+    call (fuel-index) fuel-eval-set-result ; inline
+
 ! -run=fuel support
 
 : fuel-startup ( -- ) "listener" run-file ; inline
diff --git a/misc/fuel/README b/misc/fuel/README
index 36415bc225..6c03c7aa01 100644
--- a/misc/fuel/README
+++ b/misc/fuel/README
@@ -1,110 +1,115 @@
-FUEL, Factor's Ultimate Emacs Library
+FUEL, Factor's Ultimate Emacs Library                              -*- org -*-
 -------------------------------------
 
 FUEL provides a complete environment for your Factor coding pleasure
 inside Emacs, including source code edition and interaction with a
 Factor listener instance running within Emacs.
 
-FUEL was started by Jose A Ortega as an extension to Ed Cavazos'
-original factor.el code.
+FUEL was started by Jose A Ortega as an extension to Eduardo Cavazos'
+original factor.el code. Eduardo is also responsible of naming the
+beast.
 
-Installation
-------------
+* Installation
 
-FUEL comes bundled with Factor's distribution. The folder misc/fuel
-contains Elisp code, and there's a fuel vocabulary in extras/fuel.
+  FUEL comes bundled with Factor's distribution. The folder misc/fuel
+  contains Elisp code, and there's a fuel vocabulary in extras/fuel.
 
-To install FUEL, either add this line to your Emacs initialisation:
+  To install FUEL, either add this line to your Emacs initialisation:
 
   (load-file "<path/to/factor/installation>/misc/fuel/fu.el")
 
-or
+  or
 
   (add-to-list load-path "<path/to/factor/installation>/fuel")
   (require 'fuel)
 
-If all you want is a major mode for editing Factor code with pretty
-font colors and indentation, without running the factor listener
-inside Emacs, you can use instead:
+  If all you want is a major mode for editing Factor code with pretty
+  font colors and indentation, without running the factor listener
+  inside Emacs, you can use instead:
 
   (add-to-list load-path "<path/to/factor/installation>/fuel")
   (setq factor-mode-use-fuel nil)
   (require 'factor-mode)
 
-Basic usage
------------
+* Basic usage
 
-If you're using the default factor binary and images locations inside
-the Factor's source tree, that should be enough to start using FUEL.
-Editing any file with the extension .factor will put you in
-factor-mode; try C-hm for a summary of available commands.
+  If you're using the default factor binary and images locations inside
+  the Factor's source tree, that should be enough to start using FUEL.
+  Editing any file with the extension .factor will put you in
+  factor-mode; try C-hm for a summary of available commands.
 
-To start the listener, try M-x run-factor.
+  To start the listener, try M-x run-factor.
 
-Many aspects of the environment can be customized:
-M-x customize-group fuel will show you how many.
+  Many aspects of the environment can be customized:
+  M-x customize-group fuel will show you how many.
 
-Quick key reference
--------------------
+* Quick key reference
 
-(Triple chords ending in a single letter <x> accept also C-<x> (e.g.
-C-cC-eC-r is the same as C-cC-er)).
+  (Triple chords ending in a single letter <x> accept also C-<x> (e.g.
+  C-cC-eC-r is the same as C-cC-er)).
 
-* In factor source files:
+*** In factor source files:
 
- - C-cz : switch to listener
- - C-co : cycle between code, tests and docs factor files
+    - C-cz : switch to listener
+    - C-co : cycle between code, tests and docs factor files
 
- - M-. : edit word at point in Emacs
- - M-TAB : complete word at point
- - C-cC-eu : update USING: line
- - C-cC-ev : edit vocabulary (M-x fuel-edit-vocabulary)
- - C-cC-ew : edit word (M-x fuel-edit-word-at-point)
- - C-cC-ed : edit word's doc (M-x fuel-edit-word-at-point)
+    - M-. : edit word at point in Emacs
+    - M-TAB : complete word at point
+    - C-cC-eu : update USING: line
+    - C-cC-ev : edit vocabulary (M-x fuel-edit-vocabulary)
+    - C-cC-ew : edit word (M-x fuel-edit-word-at-point)
+    - C-cC-ed : edit word's doc (M-x fuel-edit-word-at-point)
 
- - C-cr, C-cC-er : eval region
- - C-M-r, C-cC-ee : eval region, extending it to definition boundaries
- - C-M-x, C-cC-ex : eval definition around point
- - C-ck, C-cC-ek : run file
+    - C-cr, C-cC-er : eval region
+    - C-M-r, C-cC-ee : eval region, extending it to definition boundaries
+    - C-M-x, C-cC-ex : eval definition around point
+    - C-ck, C-cC-ek : run file
 
- - C-cC-da : toggle autodoc mode
- - C-cC-dd : help for word at point
- - C-cC-ds : short help word at point
- - C-cC-de : show stack effect of current sexp (with prefix, region)
+    - C-cC-da : toggle autodoc mode
+    - C-cC-dd : help for word at point
+    - C-cC-ds : short help word at point
+    - C-cC-de : show stack effect of current sexp (with prefix, region)
+    - C-cC-dp : find words containing given substring (M-x fuel-apropos)
 
- - C-cM-<, C-cC-d< : show callers of word at point
- - C-cM->, C-cC-d> : show callees of word at point
+    - C-cM-<, C-cC-d< : show callers of word at point
+    - C-cM->, C-cC-d> : show callees of word at point
 
-* In the listener:
+*** In the listener:
 
- - TAB : complete word at point
- - M-. : edit word at point in Emacs
- - C-ca : toggle autodoc mode
- - C-cs : toggle stack mode
- - C-cv : edit vocabulary
- - C-ch : help for word at point
- - C-ck : run file
+    - TAB : complete word at point
+    - M-. : edit word at point in Emacs
+    - C-ca : toggle autodoc mode
+    - C-cp : find words containing given substring (M-x fuel-apropos)
+    - C-cs : toggle stack mode
+    - C-cv : edit vocabulary
+    - C-ch : help for word at point
+    - C-ck : run file
 
-* In the debugger (it pops up upon eval/compilation errors):
+*** In the debugger (it pops up upon eval/compilation errors):
 
- - g : go to error
- - <digit> : invoke nth restart
- - w/e/l : invoke :warnings, :errors, :linkage
- - q : bury buffer
+    - g : go to error
+    - <digit> : invoke nth restart
+    - w/e/l : invoke :warnings, :errors, :linkage
+    - q : bury buffer
 
-* In the Help browser:
+*** In the help browser:
 
- - h : help for word at point
- - f/b : next/previous page
- - SPC/S-SPC : scroll up/down
- - TAB/S-TAB : next/previous link
- - c : clean browsing history
- - M-. : edit word at point in Emacs
- - C-cz : switch to listener
- - q : bury buffer
+    - h : help for word at point
+    - a : find words containing given substring (M-x fuel-apropos)
+    - ba : bookmark current page
+    - bb : display bookmarks
+    - bd : delete bookmark at point
+    - n/p : next/previous page
+    - SPC/S-SPC : scroll up/down
+    - TAB/S-TAB : next/previous link
+    - r : refresh page
+    - c : clean browsing history
+    - M-. : edit word at point in Emacs
+    - C-cz : switch to listener
+    - q : bury buffer
 
-* In crossref buffers
+*** In crossref buffers
 
- - TAB/BACKTAB : navigate links
- - RET/mouse click : follow link
- - q : bury buffer
+    - TAB/BACKTAB : navigate links
+    - RET/mouse click : follow link
+    - q : bury buffer
diff --git a/misc/fuel/fuel-help.el b/misc/fuel/fuel-help.el
index dc40463362..12091ea399 100644
--- a/misc/fuel/fuel-help.el
+++ b/misc/fuel/fuel-help.el
@@ -17,6 +17,7 @@
 (require 'fuel-eval)
 (require 'fuel-markup)
 (require 'fuel-autodoc)
+(require 'fuel-xref)
 (require 'fuel-completion)
 (require 'fuel-font-lock)
 (require 'fuel-popup)
@@ -41,6 +42,11 @@
   :type 'integer
   :group 'fuel-help)
 
+(defcustom fuel-help-bookmarks nil
+  "Bookmars. Maintain this list using the help browser."
+  :type 'list
+  :group 'fuel-help)
+
 
 ;;; Help browser history:
 
@@ -49,13 +55,17 @@
         (make-ring fuel-help-history-cache-size)   ; previous
         (make-ring fuel-help-history-cache-size))) ; next
 
-(defvar fuel-help--history (fuel-help--make-history))
+(defsubst fuel-help--history-current ()
+  (car fuel-help--history))
 
-(defun fuel-help--history-push (term)
-  (when (and (car fuel-help--history)
-             (not (string= (caar fuel-help--history) (car term))))
-    (ring-insert (nth 1 fuel-help--history) (car fuel-help--history)))
-  (setcar fuel-help--history term))
+(defun fuel-help--history-push (link)
+  (unless (equal link (car fuel-help--history))
+    (let ((next (fuel-help--history-next)))
+      (unless (equal link next)
+        (when next (fuel-help--history-previous))
+        (ring-insert (nth 1 fuel-help--history) (car fuel-help--history))
+        (setcar fuel-help--history link))))
+  link)
 
 (defun fuel-help--history-next ()
   (when (not (ring-empty-p (nth 2 fuel-help--history)))
@@ -69,6 +79,25 @@
       (ring-insert (nth 2 fuel-help--history) (car fuel-help--history)))
     (setcar fuel-help--history (ring-remove (nth 1 fuel-help--history) 0))))
 
+(defvar fuel-help--history (fuel-help--make-history))
+
+
+;;; Page cache:
+
+(defun fuel-help--history-current-content ()
+  (fuel-help--cache-get (car fuel-help--history)))
+
+(defvar fuel-help--cache (make-hash-table :weakness 'key :test 'equal))
+
+(defsubst fuel-help--cache-get (name)
+  (gethash name fuel-help--cache))
+
+(defsubst fuel-help--cache-insert (name str)
+  (puthash name str fuel-help--cache))
+
+(defsubst fuel-help--cache-clear ()
+  (clrhash fuel-help--cache))
+
 
 ;;; Fuel help buffer and internals:
 
@@ -78,6 +107,9 @@
 
 (defvar fuel-help--prompt-history nil)
 
+(make-local-variable
+ (defvar fuel-help--buffer-link nil))
+
 (defun fuel-help--read-word (see)
   (let* ((def (fuel-syntax-symbol-at-point))
          (prompt (format "See%s help on%s: " (if see " short" "")
@@ -101,39 +133,90 @@
                (res (fuel-eval--retort-result ret)))
           (if (not res)
               (message "No help for '%s'" def)
-            (fuel-help--insert-contents def res)))))))
+            (fuel-help--insert-contents (list def def 'word) res)))))))
 
 (defun fuel-help--get-article (name label)
-  (message "Retriving article ...")
+  (message "Retrieving article ...")
   (let* ((cmd `(:fuel* ((,name fuel-get-article)) "fuel" t))
          (ret (fuel-eval--send/wait cmd 2000))
          (res (fuel-eval--retort-result ret)))
-    (fuel-help--insert-contents label res)
-    (message "")))
+    (if (not res)
+        (message "Article '%s' not found" label)
+      (fuel-help--insert-contents (list name label 'article) res)
+      (message ""))))
 
-(defun fuel-help--follow-link (label link type)
-  (let ((fuel-help-always-ask nil))
-    (cond ((eq type 'word) (fuel-help--word-help nil link))
-          ((eq type 'article) (fuel-help--get-article link label))
-          (t (message (format "Links of type %s not yet implemented" type))))))
+(defun fuel-help--get-vocab (name)
+  (message "Retrieving vocabulary help ...")
+  (let* ((cmd `(:fuel* ((,name fuel-vocab-help)) "fuel" (,name)))
+         (ret (fuel-eval--send/wait cmd 2000))
+         (res (fuel-eval--retort-result ret)))
+    (if (not res)
+        (message "No help available for vocabulary '%s'" name)
+      (fuel-help--insert-contents (list name name 'vocab) res)
+      (message ""))))
 
-(defun fuel-help--insert-contents (def art &optional nopush)
+(defun fuel-help--follow-link (link label type &optional no-cache)
+  (let* ((llink (list link label type))
+         (cached (and (not no-cache) (fuel-help--cache-get llink))))
+    (if (not cached)
+        (let ((fuel-help-always-ask nil))
+          (cond ((eq type 'word) (fuel-help--word-help nil link))
+                ((eq type 'article) (fuel-help--get-article link label))
+                ((eq type 'vocab) (fuel-help--get-vocab link))
+                ((eq type 'bookmarks) (fuel-help-display-bookmarks))
+                (t (error "Links of type %s not yet implemented" type))))
+      (fuel-help--insert-contents llink cached))))
+
+(defun fuel-help--insert-contents (key content)
   (let ((hb (fuel-help--buffer))
         (inhibit-read-only t)
         (font-lock-verbose nil))
     (set-buffer hb)
     (erase-buffer)
-    (if (stringp art)
-        (insert art)
-      (fuel-markup--print art)
-      (fuel-markup--insert-newline))
-    (unless nopush
-      (fuel-help--history-push (cons def (buffer-string))))
+    (if (stringp content)
+        (insert content)
+      (fuel-markup--print content)
+      (fuel-markup--insert-newline)
+      (fuel-help--cache-insert key (buffer-string)))
+    (fuel-help--history-push key)
+    (setq fuel-help--buffer-link key)
     (set-buffer-modified-p nil)
     (fuel-popup--display)
     (goto-char (point-min))
     (message "")))
 
+
+;;; Bookmarks:
+
+(defun fuel-help-bookmark-page ()
+  "Add current help page to bookmarks."
+  (interactive)
+  (let ((link fuel-help--buffer-link))
+    (unless link (error "No link associated to this page"))
+    (add-to-list 'fuel-help-bookmarks link)
+    (customize-save-variable 'fuel-help-bookmarks fuel-help-bookmarks)
+    (message "Bookmark '%s' saved" (cadr link))))
+
+(defun fuel-help-delete-bookmark ()
+  "Delete link at point from bookmarks."
+  (interactive)
+  (let ((link (fuel-markup--link-at-point)))
+    (unless link (error "No link at point"))
+    (unless (member link fuel-help-bookmarks)
+      (error "'%s' is not bookmarked" (cadr link)))
+    (customize-save-variable 'fuel-help-bookmarks
+                             (remove link fuel-help-bookmarks))
+    (message "Bookmark '%s' delete" (cadr link))
+    (fuel-help-display-bookmarks)))
+
+(defun fuel-help-display-bookmarks ()
+  "Display bookmarked pages."
+  (interactive)
+  (let ((links (mapcar (lambda (l) (cons '$subsection l)) fuel-help-bookmarks)))
+    (unless links (error "No links to display"))
+    (fuel-help--insert-contents '("bookmarks" "Bookmars" bookmarks)
+                                `(article "Bookmarks" ,links))))
+
 
 ;;; Interactive help commands:
 
@@ -151,26 +234,30 @@ buffer."
 (defun fuel-help-next ()
   "Go to next page in help browser."
   (interactive)
-  (let ((item (fuel-help--history-next))
-        (fuel-help-always-ask nil))
-    (unless item
-      (error "No next page"))
-    (fuel-help--insert-contents (car item) (cdr item) t)))
+  (let ((item (fuel-help--history-next)))
+    (unless item (error "No next page"))
+    (apply 'fuel-help--follow-link item)))
 
 (defun fuel-help-previous ()
-  "Go to next page in help browser."
+  "Go to previous page in help browser."
   (interactive)
-  (let ((item (fuel-help--history-previous))
-        (fuel-help-always-ask nil))
-    (unless item
-      (error "No previous page"))
-    (fuel-help--insert-contents (car item) (cdr item) t)))
+  (let ((item (fuel-help--history-previous)))
+    (unless item (error "No previous page"))
+    (apply 'fuel-help--follow-link item)))
+
+(defun fuel-help-refresh ()
+  "Refresh the contents of current page."
+  (interactive)
+  (when fuel-help--buffer-link
+    (apply 'fuel-help--follow-link (append fuel-help--buffer-link '(t)))))
 
 (defun fuel-help-clean-history ()
   "Clean up the help browser cache of visited pages."
   (interactive)
   (when (y-or-n-p "Clean browsing history? ")
-    (setq fuel-help--history (fuel-help--make-history)))
+    (fuel-help--cache-clear)
+    (setq fuel-help--history (fuel-help--make-history))
+    (fuel-help-refresh))
   (message ""))
 
 
@@ -180,13 +267,15 @@ buffer."
   (let ((map (make-sparse-keymap)))
     (suppress-keymap map)
     (set-keymap-parent map button-buffer-map)
-    (define-key map "b" 'fuel-help-previous)
+    (define-key map "a" 'fuel-apropos)
+    (define-key map "ba" 'fuel-help-bookmark-page)
+    (define-key map "bb" 'fuel-help-display-bookmarks)
+    (define-key map "bd" 'fuel-help-delete-bookmark)
     (define-key map "c" 'fuel-help-clean-history)
-    (define-key map "f" 'fuel-help-next)
     (define-key map "h" 'fuel-help)
-    (define-key map "l" 'fuel-help-previous)
-    (define-key map "p" 'fuel-help-previous)
     (define-key map "n" 'fuel-help-next)
+    (define-key map "p" 'fuel-help-previous)
+    (define-key map "r" 'fuel-help-refresh)
     (define-key map (kbd "SPC")  'scroll-up)
     (define-key map (kbd "S-SPC") 'scroll-down)
     (define-key map "\M-." 'fuel-edit-word-at-point)
@@ -207,12 +296,7 @@ buffer."
   (set-syntax-table fuel-syntax--syntax-table)
   (setq mode-name "FUEL Help")
   (setq major-mode 'fuel-help-mode)
-
   (setq fuel-markup--follow-link-function 'fuel-help--follow-link)
-
-  (setq fuel-autodoc-mode-string "")
-  (fuel-autodoc-mode)
-
   (setq buffer-read-only t))
 
 
diff --git a/misc/fuel/fuel-listener.el b/misc/fuel/fuel-listener.el
index eb159eb56e..ecb47f68a2 100644
--- a/misc/fuel/fuel-listener.el
+++ b/misc/fuel/fuel-listener.el
@@ -1,6 +1,6 @@
 ;;; fuel-listener.el --- starting the fuel listener
 
-;; Copyright (C) 2008  Jose Antonio Ortega Ruiz
+;; Copyright (C) 2008, 2009  Jose Antonio Ortega Ruiz
 ;; See http://factorcode.org/license.txt for BSD license.
 
 ;; Author: Jose Antonio Ortega Ruiz <jao@gnu.org>
@@ -15,6 +15,7 @@
 
 (require 'fuel-stack)
 (require 'fuel-completion)
+(require 'fuel-xref)
 (require 'fuel-eval)
 (require 'fuel-connection)
 (require 'fuel-syntax)
@@ -169,6 +170,7 @@ buffer."
 (define-key fuel-listener-mode-map "\C-ca" 'fuel-autodoc-mode)
 (define-key fuel-listener-mode-map "\C-ch" 'fuel-help)
 (define-key fuel-listener-mode-map "\C-cs" 'fuel-stack-mode)
+(define-key fuel-listener-mode-map "\C-cp" 'fuel-apropos)
 (define-key fuel-listener-mode-map "\M-." 'fuel-edit-word-at-point)
 (define-key fuel-listener-mode-map "\C-cv" 'fuel-edit-vocabulary)
 (define-key fuel-listener-mode-map "\C-c\C-v" 'fuel-edit-vocabulary)
diff --git a/misc/fuel/fuel-markup.el b/misc/fuel/fuel-markup.el
index 0c83c74040..a2c94d4f4a 100644
--- a/misc/fuel/fuel-markup.el
+++ b/misc/fuel/fuel-markup.el
@@ -52,29 +52,41 @@
 (defun fuel-markup--follow-link (button)
   (when fuel-markup--follow-link-function
     (funcall fuel-markup--follow-link-function
-             (button-label button)
              (button-get button 'markup-link)
+             (button-get button 'markup-label)
              (button-get button 'markup-link-type))))
 
-(defun fuel-markup--echo-link (label link type)
+(defun fuel-markup--echo-link (link label type)
   (message "Link %s pointing to %s named %s" label type link))
 
 (defun fuel-markup--insert-button (label link type)
-  (insert-text-button (format "%s" label)
-                      :type 'fuel-markup--button
-                      'markup-link (format "%s" link)
-                      'markup-link-type type))
+  (let ((label (format "%s" label))
+        (link (format "%s" link)))
+    (insert-text-button label
+                        :type 'fuel-markup--button
+                        'markup-link link
+                        'markup-label label
+                        'markup-link-type type
+                        'help-echo (format "%s (%s)" label type))))
 
 (defun fuel-markup--article-title (name)
   (fuel-eval--retort-result
    (fuel-eval--send/wait `(:fuel* ((,name fuel-article-title :get)) "fuel"))))
 
+(defun fuel-markup--link-at-point ()
+  (let ((button (condition-case nil (forward-button 0) (error nil))))
+    (when button
+      (list (button-get button 'markup-link)
+            (button-get button 'markup-label)
+            (button-get button 'markup-link-type)))))
+
 
 ;;; Markup printers:
 
 (defconst fuel-markup--printers
   '(($class-description . fuel-markup--class-description)
     ($code . fuel-markup--code)
+    ($command . fuel-markup--command)
     ($contract . fuel-markup--contract)
     ($curious . fuel-markup--curious)
     ($definition . fuel-markup--definition)
@@ -86,6 +98,7 @@
     ($example . fuel-markup--example)
     ($examples . fuel-markup--examples)
     ($heading . fuel-markup--heading)
+    ($index . fuel-markup--index)
     ($instance . fuel-markup--instance)
     ($io-error . fuel-markup--io-error)
     ($link . fuel-markup--link)
@@ -98,6 +111,7 @@
     ($nl . fuel-markup--newline)
     ($notes . fuel-markup--notes)
     ($parsing-note . fuel-markup--parsing-note)
+    ($predicate . fuel-markup--predicate)
     ($prettyprinting-note . fuel-markup--prettyprinting-note)
     ($quotation . fuel-markup--quotation)
     ($references . fuel-markup--references)
@@ -142,6 +156,11 @@
         ((symbolp e) (fuel-markup--print (list '$link e)))
         (t (insert (format "\n%S\n" e)))))
 
+(defun fuel-markup--print-str (e)
+  (with-temp-buffer
+    (fuel-markup--print e)
+    (buffer-string)))
+
 (defun fuel-markup--maybe-nl ()
   (setq fuel-markup--maybe-nl (point)))
 
@@ -190,6 +209,12 @@
   (fuel-markup--link (cons '$link (cdr e)))
   (fuel-markup--maybe-nl))
 
+(defun fuel-markup--vocab-subsection (e)
+  (fuel-markup--insert-nl-if-nb)
+  (insert "  - ")
+  (fuel-markup--vocab-link (cons '$vocab-link (cdr e)))
+  (fuel-markup--maybe-nl))
+
 (defun fuel-markup--newline (e)
   (fuel-markup--insert-newline)
   (newline))
@@ -214,10 +239,8 @@
     (insert (cadr e))))
 
 (defun fuel-markup--snippet (e)
-  (let ((snip (cadr e)))
-    (if (stringp snip)
-        (insert (fuel-font-lock--factor-str snip))
-      (fuel-markup--print snip))))
+  (let ((snip (format "%s" (cdr e))))
+    (insert (fuel-font-lock--factor-str snip))))
 
 (defun fuel-markup--code (e)
   (fuel-markup--insert-nl-if-nb)
@@ -229,6 +252,9 @@
     (newline))
   (newline))
 
+(defun fuel-markup--command (e)
+  (fuel-markup--snippet (list '$snippet (nth 3 e))))
+
 (defun fuel-markup--syntax (e)
   (fuel-markup--insert-heading "Syntax")
   (fuel-markup--print (cons '$code (cdr e)))
@@ -236,30 +262,46 @@
 
 (defun fuel-markup--examples (e)
   (fuel-markup--insert-heading "Examples")
-  (fuel-markup--print (cdr e)))
+  (dolist (ex (cdr e))
+    (fuel-markup--print ex)
+    (newline)))
 
 (defun fuel-markup--example (e)
-  (fuel-markup--print (cons '$code (cdr e))))
+  (fuel-markup--snippet (list '$snippet (cadr e))))
 
 (defun fuel-markup--markup-example (e)
-  (fuel-markup--print (cons '$code (cdr e))))
+  (fuel-markup--snippet (cons '$snippet (cadr e))))
 
 (defun fuel-markup--link (e)
-  (let* ((link (cadr e))
-         (type (if (symbolp link) 'word 'article))
-         (label (or (and (eq type 'article)
+  (let* ((link (nth 1 e))
+         (type (or (nth 3 e) (if (symbolp link) 'word 'article)))
+         (label (or (nth 2 e)
+                    (and (eq type 'article)
                          (fuel-markup--article-title link))
                     link)))
     (fuel-markup--insert-button label link type)))
 
 (defun fuel-markup--links (e)
   (dolist (link (cdr e))
-    (insert " ")
     (fuel-markup--link (list '$link link))
-    (insert " ")))
+    (insert ", "))
+  (delete-backward-char 2))
 
-(defun fuel-markup--vocab-subsection (e)
-  (insert (format " %S " e)))
+(defun fuel-markup--index-quotation (q)
+  (cond ((null q) null)
+        ((listp q) (vconcat (mapcar 'fuel-markup--index-quotation q)))
+        (t q)))
+
+(defun fuel-markup--index (e)
+  (let* ((q (fuel-markup--index-quotation (cadr e)))
+         (cmd `(:fuel* ((,q fuel-index)) "fuel"
+                       ("builtins" "help" "help.topics" "classes"
+                        "classes.builtin" "classes.tuple"
+                        "classes.singleton" "classes.union"
+                        "classes.intersection" "classes.predicate")))
+         (subs (fuel-eval--retort-result (fuel-eval--send/wait cmd 200))))
+    (when subs
+      (fuel-markup--print subs))))
 
 (defun fuel-markup--vocab-link (e)
   (fuel-markup--insert-button (cadr e) (cadr e) 'vocab))
@@ -271,8 +313,8 @@
     (insert " ")))
 
 (defun fuel-markup--vocabulary (e)
-  (fuel-markup--insert-heading "Vocabulary:" t)
-  (insert " " (cadr e))
+  (fuel-markup--insert-heading "Vocabulary: " t)
+  (fuel-markup--vocab-link (cons '$vocab-link (cdr e)))
   (newline))
 
 (defun fuel-markup--list (e)
@@ -314,6 +356,13 @@
     (fuel-markup--print (cdr val))
     (newline)))
 
+(defun fuel-markup--predicate (e)
+  (fuel-markup--values '($values ("object" object) ("?" "a boolean")))
+  (let ((word (make-symbol (substring (format "%s" (cadr e)) 0 -1))))
+  (fuel-markup--description
+   `($description "Tests if the object is an instance of the "
+                  ($link ,word) " class."))))
+
 (defun fuel-markup--side-effects (e)
   (fuel-markup--insert-heading "Side effects")
   (insert "Modifies ")
@@ -343,12 +392,19 @@
 
 (defun fuel-markup--references (e)
   (fuel-markup--insert-heading "References")
-  (fuel-markup--links (cons '$links (cdr e))))
+  (dolist (ref (cdr e))
+    (if (listp ref)
+        (fuel-markup--print ref)
+      (fuel-markup--subsection (list '$subsection ref)))))
 
 (defun fuel-markup--see-also (e)
   (fuel-markup--insert-heading "See also")
   (fuel-markup--links (cons '$links (cdr e))))
 
+(defun fuel-markup--related (e)
+  (fuel-markup--insert-heading "See also")
+  (fuel-markup--links (cons '$links (cadr e))))
+
 (defun fuel-markup--shuffle (e)
   (insert "\nShuffle word. Re-arranges the stack "
           "according to the stack effect pattern.")
@@ -376,6 +432,12 @@
   (fuel-markup--print (cdr elem))
   (fuel-markup--insert-newline))
 
+(defun fuel-markup--quotation (e)
+  (insert "a ")
+  (fuel-markup--link (list '$link 'quotation 'quotation 'word))
+  (insert " with stack effect ")
+  (fuel-markup--snippet (list '$snippet (nth 1 e))))
+
 (defun fuel-markup--warning (e)
   (fuel-markup--elem-with-heading e "Warning"))
 
@@ -394,9 +456,6 @@
 (defun fuel-markup--contract (e)
   (fuel-markup--elem-with-heading e "Generic word contract"))
 
-(defun fuel-markup--related (e)
-  (fuel-markup--elem-with-heading e "See also"))
-
 (defun fuel-markup--errors (e)
   (fuel-markup--elem-with-heading e "Errors"))
 
@@ -404,14 +463,17 @@
   (fuel-markup--elem-with-heading e "Notes"))
 
 (defun fuel-markup--see (e)
-  (insert (format " %S " e)))
+  (let* ((word (nth 1 e))
+         (cmd (and word `(:fuel* (,(format "%s" word) fuel-word-see) "fuel" t)))
+         (res (and cmd
+                   (fuel-eval--retort-result (fuel-eval--send/wait cmd 100)))))
+    (if res
+        (fuel-markup--code (list '$code res))
+      (fuel-markup--snippet (list '$snippet word)))))
 
 (defun fuel-markup--synopsis (e)
   (insert (format " %S " e)))
 
-(defun fuel-markup--quotation (e)
-  (insert (format " %S " e)))
-
 
 (provide 'fuel-markup)
 ;;; fuel-markup.el ends here
diff --git a/misc/fuel/fuel-mode.el b/misc/fuel/fuel-mode.el
index 1074f60f5f..df06584fab 100644
--- a/misc/fuel/fuel-mode.el
+++ b/misc/fuel/fuel-mode.el
@@ -1,6 +1,6 @@
 ;;; fuel-mode.el -- Minor mode enabling FUEL niceties
 
-;; Copyright (C) 2008 Jose Antonio Ortega Ruiz
+;; Copyright (C) 2008, 2009 Jose Antonio Ortega Ruiz
 ;; See http://factorcode.org/license.txt for BSD license.
 
 ;; Author: Jose Antonio Ortega Ruiz <jao@gnu.org>
@@ -224,6 +224,11 @@ With prefix argument, ask for word."
       (message "Looking up %s's callees ..." word)
       (fuel-xref--show-callees word))))
 
+(defun fuel-apropos (str)
+  "Show a list of words containing the given substring."
+  (interactive "MFind words containing: ")
+  (message "Looking up %s's references ..." str)
+  (fuel-xref--apropos str))
 
 ;;; Minor mode definition:
 
@@ -289,6 +294,7 @@ interacting with a factor listener is at your disposal.
 (fuel-mode--key ?d ?> 'fuel-show-callees)
 (fuel-mode--key ?d ?< 'fuel-show-callers)
 (fuel-mode--key ?d ?a 'fuel-autodoc-mode)
+(fuel-mode--key ?d ?p 'fuel-apropos)
 (fuel-mode--key ?d ?d 'fuel-help)
 (fuel-mode--key ?d ?e 'fuel-stack-effect-sexp)
 (fuel-mode--key ?d ?s 'fuel-help-short)
diff --git a/misc/fuel/fuel-xref.el b/misc/fuel/fuel-xref.el
index eb57c98ce2..31f8bcb69b 100644
--- a/misc/fuel/fuel-xref.el
+++ b/misc/fuel/fuel-xref.el
@@ -75,11 +75,10 @@ cursor at the first ocurrence of the used word."
 (defvar fuel-xref--help-string "(Press RET or click to follow crossrefs)")
 
 (defun fuel-xref--title (word cc count)
-  (let ((cc (if cc "using" "used by")))
-    (put-text-property 0 (length word) 'font-lock-face 'bold word)
-    (cond ((zerop count) (format "No known words %s %s" cc word))
-          ((= 1 count) (format "1 word %s %s:" cc word))
-          (t (format "%s words %s %s:" count cc word)))))
+  (put-text-property 0 (length word) 'font-lock-face 'bold word)
+  (cond ((zerop count) (format "No known words %s %s" cc word))
+        ((= 1 count) (format "1 word %s %s:" cc word))
+        (t (format "%s words %s %s:" count cc word))))
 
 (defun fuel-xref--insert-ref (ref)
   (when (and (stringp (first ref))
@@ -124,12 +123,17 @@ cursor at the first ocurrence of the used word."
 (defun fuel-xref--show-callers (word)
   (let* ((cmd `(:fuel* (((:quote ,word) fuel-callers-xref))))
          (res (fuel-eval--retort-result (fuel-eval--send/wait cmd))))
-    (fuel-xref--fill-and-display word t res)))
+    (fuel-xref--fill-and-display word "using" res)))
 
 (defun fuel-xref--show-callees (word)
   (let* ((cmd `(:fuel* (((:quote ,word) fuel-callees-xref))))
          (res (fuel-eval--retort-result (fuel-eval--send/wait cmd))))
-    (fuel-xref--fill-and-display word nil res)))
+    (fuel-xref--fill-and-display word "used by" res)))
+
+(defun fuel-xref--apropos (str)
+  (let* ((cmd `(:fuel* ((,str fuel-apropos-xref))))
+         (res (fuel-eval--retort-result (fuel-eval--send/wait cmd))))
+    (fuel-xref--fill-and-display str "containing" res)))
 
 
 ;;; Xref mode: