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:, 2015), the detected RNA corresponded to small RNAs < 200 nt according to their size distribution pattern, while in mammalian EVs RNA > 200 nt has been also detected (Valadi et al., 2007; Crescitelli et al., 2013).
Category: