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:This discrepancy could be explained as follows: prr5-1 shows a weaker period phenotype than toc1, and the accumulation of PRR5 does affect period length (Sato et al., 2002; Yamamoto et al., 2003).
Category: