diff --git a/book/_config.yml b/book/_config.yml
index fbf91c9..85b7326 100644
--- a/book/_config.yml
+++ b/book/_config.yml
@@ -37,6 +37,11 @@ sphinx:
           thebe: true
     html_show_copyright: false
     html_last_updated_fmt: '%B %-d, %Y'
+    bibtex_default_style: myapastyle
+    bibtex_reference_style: author_year_round
+  local_extensions:
+    apastyle: _ext/
+    bracket_citation_style: _ext/
 
 bibtex_bibfiles: 
   - references.bib
\ No newline at end of file
diff --git a/book/credits.md b/book/credits.md
index a46413e..f194b18 100644
--- a/book/credits.md
+++ b/book/credits.md
@@ -31,7 +31,7 @@ Ths doesn't include small contributions from various people from within and outs
 
 Parts of this book are taken from other external resources. If an author is not listed on a particular page, it is by the Authors. The following pages are not edited by the TeachBooks Team:
 
-- [](external/latex-to-markdown-conversion/README.md) {cite:ts}`timon_latex`, [BSD 3-clause license](https://opensource.org/license/BSD-3-Clause).
+- [](external/latex-to-markdown-conversion/README.md) {cite:t}`timon_latex`, [BSD 3-clause license](https://opensource.org/license/BSD-3-Clause).
 
 ## Acknowledgements
 Big thanks to the various colleagues and teaching assistant part of the [TeachBooks](https://teachbooks.io/) for developing tools and providing support to improve this book.
diff --git a/requirements.txt b/requirements.txt
index 0a63bae..a3917fa 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -10,3 +10,5 @@ sphinx-image-inverter
 
 --extra-index-url https://gitlab.tudelft.nl/api/v4/projects/11239/packages/pypi/simple
 sphinx-thebe ~= 0.9.9
+
+docutils==0.17.1
\ No newline at end of file