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:Thus, cephamycin biosynthesis may be limited by the flux of L-lysine, which regulates expression of the lat gene (Fang et al. 1996; Rius et al. 1996; Romero et al. 1997).
Category: