Currently, the logback-acces documentation (located at http://logback.qos.ch/access.html#configuration ) states twice that the "combined" format has the following format:
%h %l %u %t "%r" %s %b "%i{Referer}" "%i{User-Agent}"
This is wrong, both from what logback uses as the real format when using "<pattern>combined</pattern>" and from what the format is "defined" to be (as defined by Apache?).