diff --git a/contributing.md b/contributing.md
index d9e8e22..a9bcaff 100644
--- a/contributing.md
+++ b/contributing.md
@@ -4,7 +4,7 @@ Please ensure your pull request adheres to the following guidelines:
 
 - Search previous suggestions before making a new one, as yours may be a duplicate.
 - Make an individual pull request for each suggestion.
-- Titles need to be [capitalized](http://grammar.yourdictionary.com/capitalization/rules-for-capitalization-in-titles.html) properly. Don't be lazy. For help with this, see [Online Capitalize Tool](https://headlinecapitalization.com).
+- Titles need to be [capitalized](http://grammar.yourdictionary.com/capitalization/rules-for-capitalization-in-titles.html) properly. Don't be lazy. For help with this, see [Online Capitalize Tool](https://headlinecapitalization.com). Use *Chicago Manual of Style* rules.
 - Keep descriptions short and simple.
 - End all descriptions with a full stop/period.
 - Order titles alphabetically within each category.