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:However, rats are able to discriminate harmful food from harmless food by their well-developed olfactory system (Kalat and Rozin 1973; Rana et al. 1975; Bhardwaj and Prakash 1982; Balakrishnan and Alexander 1985).
Category: