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:…highly diverse gene cassettes (VAR; Vibrio anguillarum repeats), mostly of unknown function, but among others toxin/antitoxin cassettes and genes involved in substrate modification or interactions with virulence factors and DNA modification, similar to in Vibrio cholera (Rowe-Magnus et al. 2003).
Category: