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:It conditions resistance to penicillin, cefotaxime, ceftazidime and aztreonam, and its activity is well inhibited by clavulanic acid, sulbactam and tazobactam [7, 8].
Category: