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:In the yeast Sac. cerevisiae, mutation in genes BNI1, BUD3, BUD6 and SPA2, which regulate polarity and proper cell development, triggers cellpolarity phenotypes (Amberg et al., 1997; Chant et al., 1995; Sagot et al., 2002; Sheu et al., 1998).
Category: