diff --git a/SystemDoc.md b/SystemDoc.md
index 3822af8b..bfbd3612 100644
--- a/SystemDoc.md
+++ b/SystemDoc.md
@@ -12,7 +12,8 @@ System Documentation for Developers
 -   [Qubes GUI virtualization protocol](/wiki/GUIdocs)
 -   [Networking in Qubes](/wiki/QubesNet)
 -   [Inter-domain file copying](/wiki/Qfilecopy)
--   [Command execution in VM (and Qubes RPC)](/wiki/Qrexec)
+-   [Command execution in VM (and Qubes RPC)](/wiki/Qrexec) ([R3/Odyssey](/wiki/Qrexec3))
+-   [Qrexec protocol details (R3/Odyssey)?](/wiki/QrexecProtocol)
 -   [Dynamic memory management in Qubes](/wiki/Qmemman)
 -   [Implementation of DisposableVMs](/wiki/DVMimpl)
 -   [​Article about disposable VMs](http://theinvisiblethings.blogspot.com/2010/06/disposable-vms.html)