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:We note that although PSIPRED was not optimized for peptides, the resulting fragment libraries showed in practice good coverage of the peptide conformational space (in concordance with a recent report by Vanhee et al. that most peptide-protein interactions can be represented by fragment sets derived from single, non-related monomer structures [17]).
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