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:Cervo et al. (1990) reported that the α2 adrenoceptor blockers idazoxan and 1-(pyrimidinyl)piperazine antagonized the effect of desipramine on immobility time in the forced-swim test in rats.
Category: