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:Furthermore, PRRs are also involved in the control of hypocotyl elongation and flowering time (Makino et al., 2002; Matsushika et al., 2002, 2007b; Sato et al., 2002; Kaczorowski and Quail, 2003; Murakami et al., 2004).
Category: