diff --git a/docs/06-data-encryption-keys.md b/docs/06-data-encryption-keys.md
index 29ec122..4d6392c 100644
--- a/docs/06-data-encryption-keys.md
+++ b/docs/06-data-encryption-keys.md
@@ -39,5 +39,6 @@ for instance in master-1 master-2; do
   scp encryption-config.yaml ${instance}:~/
 done
 ```
+Reference: https://kubernetes.io/docs/tasks/administer-cluster/encrypt-data/#encrypting-your-data
 
 Next: [Bootstrapping the etcd Cluster](07-bootstrapping-etcd.md)