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:…thus making the effects of largemouth bass indistinguishable from those of the other experimental manipulations (Hrbáček et al., 1961; Shapiro & Wright, 1984;
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Wagner, 1986; Carpenter et al., 1987, Hanson & Butler, 1990; Hanson & Butler, 1994a, b; McQueen et al., 2001; Albright et al., 2004).
Category: