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:The unique hydrogen bonding pattern and the small variation in the derived geometrical restraints provide the foundation for the previous assignment algorithms that use either hydrogen bond (DSSP(Dictionary of Secondary Structure of Proteins) [4], STRIDE [5] and SECSTR [6] and SST [7]) or geometrical restraint as inputs.
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