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:Macrobenthic organisms were classified into five different feeding groups: detritivores (surface-deposit feeders, SDF; suspension feeders, SF; subsurfacedeposit feeders, SSDF), herbivores (He) and predators (PR), according to Bianchi & Morri (1985), Gambi & Giangrande (1985), Scipione (1989), Russo (1989), Russo et al. (1985), Gambi et al.
Category: