diff --git a/book/_toc.yml b/book/_toc.yml
index e2c0691..5dd4daa 100644
--- a/book/_toc.yml
+++ b/book/_toc.yml
@@ -48,6 +48,10 @@ parts:
         sections:
         - file: external/mechanics-BSc/book/support_internal_forces/internal_forces_truss/zero-force
         - file: external/mechanics-BSc/book/support_internal_forces/internal_forces_truss/cross_section
+      - file: external/mechanics-BSc/book/support_internal_forces/internal_forces_beam/intro
+        sections:
+        - file: external/mechanics-BSc/book/support_internal_forces/internal_forces_beam/zero-force
+        - file: external/mechanics-BSc/book/support_internal_forces/internal_forces_beam/cross_section
     - file: week_2/session_2/intro
 - caption: Miscellaneous
   chapters:
diff --git a/book/external/mechanics-BSc b/book/external/mechanics-BSc
index 80b28ad..13b9dc9 160000
--- a/book/external/mechanics-BSc
+++ b/book/external/mechanics-BSc
@@ -1 +1 @@
-Subproject commit 80b28adab50477d780b42eebdbe8fdf45ebbc81e
+Subproject commit 13b9dc99a8106db8f29952b967bd5dca6f0a2000