diff --git a/extra/math/combinatorics/authors.txt b/basis/math/combinatorics/authors.txt similarity index 100% rename from extra/math/combinatorics/authors.txt rename to basis/math/combinatorics/authors.txt diff --git a/extra/math/combinatorics/combinatorics-docs.factor b/basis/math/combinatorics/combinatorics-docs.factor similarity index 100% rename from extra/math/combinatorics/combinatorics-docs.factor rename to basis/math/combinatorics/combinatorics-docs.factor diff --git a/extra/math/combinatorics/combinatorics-tests.factor b/basis/math/combinatorics/combinatorics-tests.factor similarity index 100% rename from extra/math/combinatorics/combinatorics-tests.factor rename to basis/math/combinatorics/combinatorics-tests.factor diff --git a/extra/math/combinatorics/combinatorics.factor b/basis/math/combinatorics/combinatorics.factor similarity index 100% rename from extra/math/combinatorics/combinatorics.factor rename to basis/math/combinatorics/combinatorics.factor diff --git a/extra/math/combinatorics/summary.txt b/basis/math/combinatorics/summary.txt similarity index 100% rename from extra/math/combinatorics/summary.txt rename to basis/math/combinatorics/summary.txt