diff --git a/book/external/mechanics-BSc b/book/external/mechanics-BSc
index d8ba029..a81e276 160000
--- a/book/external/mechanics-BSc
+++ b/book/external/mechanics-BSc
@@ -1 +1 @@
-Subproject commit d8ba029dd4045ae2fffe18e4199ee442426c1d49
+Subproject commit a81e27640d21245610c1cd17e1dde36460f1bec0