diff --git a/2021/DETAILS.md b/2021/DETAILS.md
index bf6e6c0..3becc21 100644
--- a/2021/DETAILS.md
+++ b/2021/DETAILS.md
@@ -50,6 +50,7 @@ Packages will be held until work time ends and then approved to open for ratings
 * Game must be created entirely within allotted time-frame
   * You should **not** be building off of an existing game (like MTG)
 * Third-party libraries and assets may be used, but core gameplay must be own work
+  * You **must document** which content is made by you and which is not
   * We **highly recommend** using git submodules for third-party libraries
 * Teams are allowed (any size allowed, participants may participate in multiple teams and individually)
 * Submissions must follow [CDB Guidelines](https://content.minetest.net/policy_and_guidance/)