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:These ultrasound studies were split between endoscopic ultrasound (EUS) [11,26,28,30,39–56] and trans-abdominal ultrasound (TAUS) [24,27,57–61], with patient numbers similar between modalities (1857 for conventional and 1875 for EUS) (Table 1).
Category: