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:, 1994; Meijer, 1996) and by RNAi (Fire et al., 1998; Tabara et al., 1998; Tabara et al., 1999; Grishok et al., 2000; Klink and Wolniak, 2000; Klink and Wolniak, 2001), using dsRNA probes derived from cyclin A and from cyclin B cDNAs that we isolated from a M.
Category: