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:This relative amount was less than in a previous report (Gatewood et al., 1987), in which approximately 15% of histone remained unreplaced in mature sperm nuclei; we suspect that our methodology for nuclear protein extraction was not optimal for analysis of histone, or that relative collection of protamine was increased by our method.
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