diff --git a/book/features/external_toc.md b/book/features/external_toc.md
index 0b594b6..c0a2a50 100644
--- a/book/features/external_toc.md
+++ b/book/features/external_toc.md
@@ -12,7 +12,7 @@ This page is useful for user type 3-5.
 
 When creating books, you might want to reuse material from other people or from other books you made. In some cases you might even want to have the exact same material into your book. You could do so by manually copying material over. However, whenever the source material is updated, you have to do that again. As an alternative, you can use the underlying git system to refer to the source file directly. This allows you to pick a specific version, or keep the most up-to-date version of it. This pages explains how to do so directly in the table of contents using the **External Content** (or **External TOC**) feature which is part of the TeachBooks Python package.
 
-Previously, this book feature was implemented using [submodules](../external/Nested-Books/README.md), but the implementation was more difficult to use. Despite this, submodules are still a widely used Git feature that can be very useful for book authors, so check out the [submodules page](../external/Nested-Books/README.md) to learn more, especially if the External TOC tool does not satisfy your needs.
+Previously, this book feature was implemented using [submodules](../external/Nested-Books/README.md), but the implementation was more difficult to use. Despite this, submodules are still a widely used Git feature that can be very useful for book authors, so check out the [submodules page](../external/Nested-Books/README.md) to learn more, especially if the External TOC tool does not satisfy your needs. Submodules have a few additional features not (yet) implemented using the External TOC.
 
 ```{warning}
 The External TOC features are not incorporated in the new deploy book workflow yet (this will happen once the workflow specifies `teachbooks>=0.2.0`).