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:2 using a previously described method (primer sequences provided in Supporting Information Table S1) (Lossin et al., 2002, 2003; Rhodes et al., 2004; Ohmori et al., 2006).
Category: