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:…results at best with some studies showing a relationship between obesity levels and distance to food outlets (Frank et al., 2004; Lopez-Zetina et al., 2006) while others have shown no relationship (Liu et al., 2002; Kelly-Schwartz et al., 2004; Burdette and Whitaker, 2004; Ewing et al., 2006).
Category: