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:Antibiotic production is perceived to provide a fitness benefit to the producer by inhibiting the growth of competing microbes (Williams and Vickers, 1986; Firn and Jones, 2000; Davelos et al., 2004a).
Category: