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 last assumption was supported by the thymic model: flutamide exposure has an opposing effect in the thymus as compared with the testis (Olsen et al., 1998; Dulos and Bagchus, 2001).
Category: