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:+1-701-777-2624; Fax +1-701-777-3894 e-mail kevin'y~ medicine'und'n~ raise for reducing rejection of organ transplants in mammals (Kino and Goto 1993).
Category: