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:(Leibold and McPeek 2006; Lekberg et al. 2013); 3) Disturbance-adapted AMF facilitate saprotrophs to degrade soil organic matter (Cheng et al.
Category: