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:…gene expression experiments on many kinds of white-rot basidiomycetes (Alves et al. 2004; Hirano et al. 2000; Irie et al. 2001; Kajita et al. 2004; Kuo et al. 2004; Li et al. 2000; Ma et al.
2001; Mayfield et al. 1994; Schuren et al. 1993; Schuren and Wessels 1994; Sollewijn Gelpke et al. 1999).
Category: