Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:In addition to the up-regulation of the EGF receptor itself in clinically localized high grade prostate cancer, we also found over-expression of MAP2K4 and the EGF activated pro-migratory RAS related gene RALA [20].
Category: