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:There is increasing evidence that cyclins play important roles in regulating cell cycle progression (Malumbres and Barbacid, 2001; Olashaw and Pledger, 2002; Murray, 2004; Chulu and Liu, 2009).
Category: