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:These methods have been used in identifying causal regulators in yeast (Friedman et al., 2000; Pe’er et al., 2001; Segal et al., 2003; Zhu et al., 2008; Bing and Hoeschele, 2005; Kulp and Jagalur, 2006) and causal mediators of disease in mice (Schadt et al., 2005).
Category: