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:Deficits were more pronounced in the right than in the left hemisphere (Ballmaier et al, 2004c), implying a possible involvement of abnormalities in inter-hemispheric information transfer in late-onset depression (Kumar et al, 2000).
Category: