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:Third, since we compared the same groups of participants also with respect to basic visuomotor tasks (Huestegge et al. 2009a), we already know that the present cannabis group exhibits deficits in basic oculomotor control.
Category: