diff --git a/trusted-team-communication.md b/trusted-team-communication.md
index 29a3cda..4e9379c 100644
--- a/trusted-team-communication.md
+++ b/trusted-team-communication.md
@@ -343,6 +343,7 @@ aspects covered.
 This work is licensed under a
 [Creative Commons Attribution-ShareAlike 4.0 International License][0].
 
+[0]: http://creativecommons.org/licenses/by-sa/4.0/
 [1]: https://en.wikipedia.org/wiki/Pretty_Good_Privacy#OpenPGP
 [2]: https://en.wikipedia.org/wiki/X.509
 [3]: https://en.wikipedia.org/wiki/S/MIME