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:Only two other studies have recorded such decreases following training, and these were of longer duration (12 24 weeks), consisted of less subjects (6 and 13) and conducted pre-HAART (MacArthur et al., 1993; Rigsby et al., 1992).
Category: