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:A couple of recent studies reported identifying large numbers of craniofacial enhancers; one study combined ChIP-seq for P300, H3K27ac, and H3K4me1 from neural crest cells derived from human embryonic stem cells (43), and the other study used ChIPseq for P300 from the whole face of E11.
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