diff --git a/book/_config.yml b/book/_config.yml
index 2805148..584ff66 100644
--- a/book/_config.yml
+++ b/book/_config.yml
@@ -40,8 +40,13 @@ sphinx:                                              # Options passed on to the
       chtml: {
         mtextInheritFont: true                       # To typeset text within math prettier
       }
+    named_colors_custom_colors: {'attributiongrey':[150,150,150]} # Defines grey colour for attribution admonition of external pages, configuration part of TeachBooks package (https://teachbooks.io/manual/features/external_toc.html)
   extra_extensions:                                  
     - teachbooks_favourites                          # Gives you a starter package of extensions to use in your book, replace with individual extensions if you prefer some extensions not to be included (https://github.com/TeachBooks/TeachBooks-Favourites)
 
+teachbooks:
+  attribution_location: top                          # Default value, sets location of attribution admonition of external pages, configuration part of TeachBooks package (https://teachbooks.io/manual/features/external_toc.html)
+  attribution_color: attributiongrey                 # Sets grey colour for attribution admonition of external pages, configuration part of TeachBooks package (https://teachbooks.io/manual/features/external_toc.html)
+
 bibtex_bibfiles: 
   - references.bib                                   # Required for references