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:Functional outcome was assessed using the system adopted by the musculoskeletal tumour Society (MSTS) for the functional evaluation of reconstructive procedures after skeletal resection [15], and a patient-reported measure of disability, the Toronto extremity salvage score (TESS) [16].
Category: