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:Because antibiotic inhibitory interactions can be highly specific among Streptomyces isolates (Davelos et al., 2004a; Vetsigian et al., 2011), the benefits of producing a single antibiotic may vary across communities.
Category: