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:Our previous studies showed that SD03-15 possesses 90.1 (nsp2) or 94.5 % (GP5) amino acid identity to SD01-08 (Fang et al., 2004, 2007).
Category: