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:, 1989), numerous inositol trisphosphate receptor genes have been identified and grouped into a family of transient receptor potential (TRP) channels (Vannier et al., 1998; Blondel et al., 1993; Maranto, 1994; Ross et al., 1992; Sudhof et al., 1991).
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