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:The CRK-SH3 is a typical class II domain that can bind the peptide motif of PxxPx+ (where + refers to a positively charged residue) (12), which well matches the sequence pattern of SecPeptide (161LGPPSPVKMP170).
Category: