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:Increasing the number of C motifs increases the amount of SHP-2 binding to CagA, although an ABCCC type of CagA appears to bind less SHP-2 than an ABD type (Higashi et al., 2002a).
Category: