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:, 1992; Murrell-Lagnado and Aldrich, 1993b) or by introducing, and altering the concentration of, an ‘‘inert’’ cation (Anderson et al., 1988; Lucchesi and Moczydlowski, 1991).
Category: