`Thanks Govvy.  But ``bitter`` is used elsewhere in Wikipedia to describe other rivalries, such as West Ham and Millwall.  I'm working on getting some qualitative and qualtatitive evidence. I also think that, as has been suggested, we need to explain why it started and has endured.  There are plenty of assertions in Wikipedia that don't have evidence, or say ``evidence required``; but no problems.  Cheeers.       `