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:1998) and to some extent in the feces (Kimura et al. 1979; Hawkins et al. 1980; Klos and Dekant 1994; Hissink et al. 1997).
Category: