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:jejuni for promoting infections in humans and chickens is a flagellum located at one or both poles of the bacterium that promotes motility (Black et al., 1988; Nachamkin et al., 1993; Wassenaar et al., 1993; Hendrixson and DiRita, 2004; Wösten et al., 2004).
Category: