"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.    

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