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:As the latest piece of information, a synthetic peptide comprising residues 33–63 of ATP7B (i.e., peptide stretch just before MBD1) was found by NMR to interact at the interface between N- and A-domains despite the usage of a high concentration of the peptide (Yu et al. 2017b).
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