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:PCR amplification of the ITS region and PS36 and P74-75 SSR markers (Cooke et al. 2000; Dorrance and Grünwald 2009; Schena et al. 2008).
Category: