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:Similar results (i.e. that greater decreases observed in g than in Amax) have also been reported in other forest species (Monson & Grant, 1989; Green & Mitchell, 1992; Zhang & Marshall, 1994) and crop plants (Ismail & Hall, 1992).
Category: