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:Up to 40–80% of human breast cancers exhibit decreased expression of Brca1 or increased activation of Akt1 (Thompson et al., 1995; Sun et al., 2001; Narod and Foulkes, 2004; Wickenden and Watson, 2010).
Category: