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:Interestingly, B. licheniformis fur (furBL) seems to have two independent PerR boxes suggesting that the regulation of furBL by PerRBL may be different from that of B. subtilis fur which has only one PerR box sequence in the promoter region (Fuangthong et al., 2002).
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