[4.0] 9335747 fix reference

[Per Buer]

commit 93357472bfdaa16b321346b067b93f80000facc3
Author: Per Buer <perbu at varnish-software.com>
Date:   Thu Feb 6 15:22:16 2014 +0100

    fix reference

diff --git a/doc/sphinx/users-guide/operation-logging.rst b/doc/sphinx/users-guide/operation-logging.rst
index 856cbfa..aaf3bb5 100644
--- a/doc/sphinx/users-guide/operation-logging.rst
+++ b/doc/sphinx/users-guide/operation-logging.rst
@@ -65,4 +65,4 @@ want to know are:
  Only list transactions where the tag matches a regular expression. If
  it matches you will get the whole transaction.
 
-For more information on this topic please see ref:`ref-varnishlog`.
+For more information on this topic please see :ref:`ref-varnishlog`.