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:On the other hand, most of the proteomics studies reported in the literature have been rested upon discrimination of meat tenderness only on the basis of Wbs (which is evaluated as the maximum shear force necessary to cut the meat perpendicular to the fibers) [2,10,19,21].
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