diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index a086873..7eb347c 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -8,6 +8,7 @@ variables:
   REGISTRY_HOST: localhost:5000
   TAG_LATEST: $REGISTRY_HOST/$CI_PROJECT_NAME/$CI_COMMIT_REF_NAME:latest
   TAG_DRAFT: $REGISTRY_HOST/$CI_PROJECT_NAME-draft/$CI_COMMIT_REF_NAME:latest
+  GIT_SUBMODULE_STRATEGY: recursive # For submodules  
 
 cache:
   paths:
@@ -72,4 +73,4 @@ deploy-draft:
     - docker run -d --restart always -p 8018:8000 --name $CI_PROJECT_NAME-draft $TAG_DRAFT
   environment:
     name: draft
-    url: https://interactivetextbooks.citg.tudelft.nl/jupyter-book-manual-draft
\ No newline at end of file
+    url: https://interactivetextbooks.citg.tudelft.nl/jupyter-book-manual-draft
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..b05a5da
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,6 @@
+[submodule "book/external/Nested-Books"]
+	path = book/external/Nested-Books
+	url = https://github.com/TeachBooks/Nested-Books.git
+[submodule "book/external/template"]
+	path = book/external/template
+	url = https://github.com/TeachBooks/template.git
diff --git a/book/_toc.yml b/book/_toc.yml
index 6c77dc0..4ff54db 100644
--- a/book/_toc.yml
+++ b/book/_toc.yml
@@ -35,6 +35,7 @@ parts:
       - file: features/remove_from_publish
       - file: features/custom_toc.md
       - file: features/custom_download.md
+      - file: external/Nested-Books/README.md
       - file: features/interactive_element.ipynb
         sections:
         - file: features/grasple.md
diff --git a/book/external/Nested-Books b/book/external/Nested-Books
new file mode 160000
index 0000000..d3f9001
--- /dev/null
+++ b/book/external/Nested-Books
@@ -0,0 +1 @@
+Subproject commit d3f900177406debf040e5c8e6b6945d047444f5d
diff --git a/book/external/template b/book/external/template
new file mode 160000
index 0000000..10eaf6c
--- /dev/null
+++ b/book/external/template
@@ -0,0 +1 @@
+Subproject commit 10eaf6cf003404f7b56638161ef7c7f7aa38af37