Yorkist Territory

A point which was brought up at the 1984 Trial of R3 was the North/South divide. Both Lancaster and York are of course in the north of England. However as we know titles conferred on nobles are not necessarily related to the place of the title.

I do have the understanding that the nobility of these times were fickle as to loyalty, but taking this into consideration I've been trying to asceratain what territories in the north, indeed in England and Wales generally (the latter I think being a strong Lancastrian stronghold), were under Yorkist control during the stabilised period of Edward IV's reign and which were under Lancastrian control,

I can find no maps of the period which show this. Can anyone help?

Alan.