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:Why our results differ from studies of tropical forests (e.g., Augspurger 1983, 1984; Augspurger and Kelly
 1984; Kitajima and Augspurger 1989) is unclear.
Category: