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:As one or two strains are sufficient to drive major changes in gastrointestinal and host metabolic profiles (Marcobal et al., 2013), we considered the possibility that the development of CDAD may also be linked to specific microbial metabolic patterns, which may help identify metabolic associations with C.
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