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:GST-53BP2(715-1005) and GST-GL(1-257) also bind DIG-PP1g1 well, whereas GST-GL(94-257), which does not contain its PP1-binding site, is unable to bind to DIG-PP1g1.
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