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:Density-dependent slow growth resulting from high densities has been implicated in previous studies examining small adult size in bluegills (Swingle and Smith 1941; Ligler 1971; Murnyak et al. 1985; Otis et al. 1998).
Category: