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:…microbial traits (Martiny et al., 2006; Green et al., 2008), competitive species interactions are argued to be important drivers of antibiotic inhibition, resistance, and resource use among Streptomyces (Wiener et al., 1998; Davelos et al., 2004a; Schlatter et al., 2013; Kinkel et al, accepted).
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