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:…largest features in the 150-ms amplitude spectrum correspond to a loss of spectral features previously attributed to hK (Rothschild et al., 1988; Dioumaev and Braiman, 1997a), and a gain of features previously attributed to hL (Rothschild et al., 1988; Walter and Braiman, 1994; Chon et al.,…
Category: