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:2003; Maier 2003), but such capability was rarely reported for cold-adapted isolates (Yakimov et al. 1999; Pini et al. 2007; Cai et al. 2014).
Category: