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:A previously described computerized force-sensitive system was used to quantify gait cycle timing, specifically the swing time and the stride-to-stride variability of swing time (Yogev et al. 2005; Bazner et al. 2000; Frenkel-Toledo et al. 2005).
Category: