[3.0] 0f07324 add link

[Tollef Fog Heen]

commit 0f0732405022fb9048c97d82a676c03c889121d3
Author: Per Buer <perbu at varnish-software.com>
Date:   Wed Jan 25 09:56:57 2012 +0100

    add link

diff --git a/doc/sphinx/tutorial/advanced_backend_servers.rst b/doc/sphinx/tutorial/advanced_backend_servers.rst
index 307f715..b4206d9 100644
--- a/doc/sphinx/tutorial/advanced_backend_servers.rst
+++ b/doc/sphinx/tutorial/advanced_backend_servers.rst
@@ -40,6 +40,8 @@ really arbitrary data. You want to send mobile devices to a different
 backend? No problem. if (req.User-agent ~ /mobile/) .... should do the
 trick. 
 
+.. _tutorial-advanced_backend_servers-directors:
+
 Directors
 ---------