diff --git a/book/_toc.yml b/book/_toc.yml
index 1f8a2c8..27aa967 100644
--- a/book/_toc.yml
+++ b/book/_toc.yml
@@ -69,6 +69,7 @@ parts:
       - file: external/JupyterBook-Patches/README.md
       - file: external/Sphinx-TUDelft-theme/README.md
       - file: external/teachbooks-sphinx-tippy/README.md
+      - file: features/apa
     - file: features/students
       sections:
       - file: external/annotater/README.md
diff --git a/book/features/_ext.zip b/book/features/_ext.zip
new file mode 100644
index 0000000..34e2f8f
Binary files /dev/null and b/book/features/_ext.zip differ
diff --git a/book/features/apa.md b/book/features/apa.md
new file mode 100644
index 0000000..a0b1a81
--- /dev/null
+++ b/book/features/apa.md
@@ -0,0 +1,69 @@
+# APA references
+
+```{admonition} User types
+:class: tip
+This page is useful for user type 4 and 5.
+```
+
+{bdg-primary}`(To be) Sphinx Extension`
+
+## Introduction
+
+This extension allows you to have APA formatting which is not a default option.
+
+
+
+## How does it work?
+Sphinx extension that inverts the colors of images and iframes in dark mode but keeps the colours recognizable. This is particularly useful for graphs in which a certain colour is mentioned in accompanying text. Item are not converted if they are marked with the `dark-light` class (recommended for photos).
+
+In more detail, the colors of the element are inverted, then the hue of the colors is shifted by 180 degrees, so the inverted colors change to their complementary hues. This flips the brightness and contrast, while keeping the hue somewhat recognizable (so a blue line will be a blue line in both ligth and dark mode). Black and white stay inverted (so white becomes black, and black becomes white), because they don’t have a hue. After this, the element blends with the background, making similar colors appear dark and very different colors appear bright. The overall effect creates high contrast between the element and the background, depending on their colors.
+
+## Installation
+To use APA-references, a python package needs to be manually loaded into your book
+
+**Step 1: Add zip file to book root**
+
+Add the zip-file [`_ext.zip`](_ext.zip) to the root of your file so that it looks like:
+
+```
+book
+├── _ext.zip
+│   ├── pybtexapastyle/
+│   ├── apastyle.py
+│   ├── bracket_citation_style.py
+├── _config.yml
+├── _toc.yml
+├── requirements.txt
+├── <book files>
+```
+
+**Step 2: Add to `requirements.txt`**
+
+Add a specific version of `docutils` to your requirements file:
+```
+docutils==0.17.1
+```
+
+**Step 3: Enable in `_config.yml`**
+
+In your `_config.yml` file, add a `bibtex_default_style`, `bybtex_reference_style` and the local extensions `apastyle` and `bracket_citation_style.py`
+```
+sphinx:
+  config:
+    ...
+    bibtex_default_style: myapastyle
+    bibtex_reference_style: author_year_round
+  local_extensions:
+    apastyle: _ext/
+    bracket_citation_style: _ext/
+  ...
+```
+
+## Usage
+All references are now made in APA-style. See for example this reference: {cite}`jason_moore` which shows up on the [references page too](../references.md)
+
+### Known issue
+During the build, warning will be raised with `... WARNING: duplicate label for keys ...`. In most cases, these warnings can be ignored.
+
+## Contribute
+This tool needs to be developed further to make it into a proper sphinx-extension. The process is described here: https://github.com/orgs/TeachBooks/projects/17. If you've ideas or questions, please reach out to us at info@teachbooks.io!
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diff --git a/book/references.bib b/book/references.bib
index 865406e..2182ee7 100644
--- a/book/references.bib
+++ b/book/references.bib
@@ -4,4 +4,11 @@
   institution ={Delft University of Technology},
   howpublished={\url{https://gitlab.tudelft.nl/opentextbooks/latex-to-markdown-conversion}},
   year={2024}
+}
+
+@misc{jason_moore,
+  title={Learn Multibody Dynamics, SymPy},
+  author={Moore, Jason},
+  url={https://moorepants.github.io/learn-multibody-dynamics/sympy.html},
+  year={2023}
 }
\ No newline at end of file