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:To avoid this force field dependence due to significant differences in point charges between AMBER variants, and obtain SASA quantities that were based solely on sequence and structure, reported SASA values were calculated using the VEGA package [28], with a probe sphere radius of 1.
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