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:…Aldrich, 1993a; Mead et al., 1998; Mullmann et al., 1999), or the channel (MacKinnon and Miller, 1989; Myers and Stampe, 2000), or by charge screening (Anderson et al., 1988; MacKinnon and Miller, 1988; Lucchesi and Moczydlowski, 1991; Giangiacomo et al., 1992, Murrell-Lagnado and Aldrich, 1993b).
Category: