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:[KOOS], pedometry studies, and gait analyses) [8, 10, 15, 23, 30], and cost-to-utility (ie, cost-to-quality adjusted lifeyears) [21, 22, 26].
Category: