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:Antibody-specific escape mutations in HIV-1 typically occur within the epitope targeted by the antibody (Andrus et al., 1998; Diskin et al., 2011; Horwitz et al., 2013; Klein et al., 2012; West et al., 2013), although allosteric mutations may also alter antibody binding in some cases (Bradley et…
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