diff --git a/Protocol.md b/Protocol.md
index 96eea1d..b772bf1 100644
--- a/Protocol.md
+++ b/Protocol.md
@@ -2,8 +2,9 @@
 * Friendica uses [DFRN](https://macgirvin.com/spec/dfrn2.pdf) as protocol. 
 * The messages use [ActivityStreams](http://activitystrea.ms/head/activity-schema.html).
 * [Webfinger](https://code.google.com/p/webfinger/wiki/WebFingerProtocol) is used for the discovery of users
-* [Salmon](https://en.wikipedia.org/wiki/Salmon_%28protocol%29)
-* [pubsubhubbub](https://code.google.com/p/pubsubhubbub/) is used for OStatus
+* [Salmon](https://en.wikipedia.org/wiki/Salmon_%28protocol%29) is used as a message exchange protocol for replies and mentions.
+* [Portable Contacts](http://portablecontacts.net/draft-spec.html) is used for friends lists.
+* [pubsubhubbub](https://code.google.com/p/pubsubhubbub/) is used for OStatus.
 
 # Ressources
 * List of used [ActivityStreams](ActivityStreams)