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:…Keddy 1989; see the review by Pausas and Austin 2001 and disturbance frequency gradients Connell 1978; Lubchenco 1978; Huston 1979; Wilson and Keddy 1988 could also be applied to the time since abandonment e.g., Peet 1978 , although the underlying factors may be different in each of these cases.
Category: