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:: +33-1-49813658 Fax: +33-1-49813685
also stimulates dopamine release from rat nucleus accumbens after i.p. administration (Ladurelle et al. 1997).
Category: