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:It was related for females of Bitis nasicornis (Marsh and Glatston, 1974), Crotalus adamanteus (Mebs and Kornalik, 1984), and Calloselasma rhodostoma (Daltry et al., 1996a, b) the production of an extra venom component that is absent from conspecific males analyzed by electrophoretic profiles.
Category: