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:However, the emergence of the cfr mobile gene has the potential to challenge oxazolidinone clinical utility as well as other antimicrobial classes (phLOPSA pattern) used in humans or animals (Arias et al., 2008; Kehrenberg and Schwartz, 2006; Kehrenberg et al., 2005, 2007; Long et al., 2006; Mendes et al,, 2008; Schwarz et al., 2000).
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