diff --git a/extra/benchmark/beust2/beust2.factor b/extra/benchmark/beust2/beust2.factor
index 8f794fb1c2..833c1fa77d 100644
--- a/extra/benchmark/beust2/beust2.factor
+++ b/extra/benchmark/beust2/beust2.factor
@@ -3,6 +3,8 @@
 USING: math math.ranges math.parser sequences kernel io locals ;
 IN: benchmark.beust2
 
+! http://crazybob.org/BeustSequence.java.html
+
 :: (count-numbers) ( remaining first value used max listener -- ? )
     10 first - [| i |
         [let* | digit [ i first + ]