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:Madsen
et al. (2004) combined these data from trained delphinids with click parameters derived from wild false killer whales and Risso’s dolphins to estimate the ranges at which different prey targets may be detected by foraging toothed whale predators.
Category: