diff --git a/book/_toc.yml b/book/_toc.yml
index d6badc4..5fa8b99 100644
--- a/book/_toc.yml
+++ b/book/_toc.yml
@@ -87,6 +87,7 @@ parts:
         - file: features/exercise_checking.ipynb
       - file: features/jupyterquiz.ipynb
       - file: external/sphinx-iframes/README.md
+      - external: https://github.com/TeachBooks/Sphinx-Indexed-Definitions/blob/manual/README.md
       - file: external/Sphinx-PRIME-applets/README.md
     - file: features/visuals.md
       sections:
diff --git a/book/references.bib b/book/references.bib
index fd81c05..65a4761 100644
--- a/book/references.bib
+++ b/book/references.bib
@@ -157,4 +157,20 @@
   url          = {https://github.com/TeachBooks/Sphinx-PRIME-applets},
   year         = {2025},
   note         = {Retrieved April 2025. MIT.}
+}
+
+@misc{teachbooks_package,
+  author       = {{TeachBooks}},
+  title        = {TeachBooks Package: Jupyter Book Wrapper},
+  url          = {https://github.com/TeachBooks/TeachBooks},
+  year         = {2024},
+  note         = {Retrieved April, 2025. MIT License.}
+}
+
+@misc{sphinx-indexed-definitions,
+  author       = {{TeachBooks}},
+  title        = {Sphinx Indexed Definitions},
+  url          = {https://github.com/TeachBooks/Sphinx-Indexed-Definitions},
+  year         = {2025},
+  note         = {Retrieved April, 2025. MIT License.}
 }
\ No newline at end of file