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:A and tiagabine in native preparations leads to significant prolongation of the postsynaptic response at GABAergic synapses (Dingledine & Korn, 1985; Roepstorff & Lambert, 1992, 1994; Thompson & Gähwiler, 1992; Isaacson, Solis & Nicoll, 1993; Draguhn & Heinemann, 1996; Engel et al., 1998; Rossi &…
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