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:Ag43 has been shown to play a role in autoaggregation and colony morphology of certain E. coli strains and may be implicated in cell adhesion and biofilm formation (Diderichsen, 1980; Owen et al., 1996; Henderson et al., 1997a; Hasman et al., 1999, 2000; Danese et al., 2000).
Category: