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:Although Soge et al. (2009) were able to amplify a fragment of 686 base pairs of the tet(M) gene in two out of 92 C. perfringens soil and water isolates that carried tetA(P) and tetB(P), the tet(M) gene has not been previously found in any clinical strain of C. perfringens that also carried tetB(P)…
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