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:Spacers specifically determine the targets of CRISPR-mediated immunity (Barrangou et al., 2007; Brouns et al., 2008; Marraffini & Sontheimer, 2008), most likely after a base-pairing recognition of the complementary sequence.
Category: