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:Environmental proteomics is beginning to reveal expressed functions within these communities (Ram et al., 2005) and to document functionally important strain variation (Lo et al., 2007; Denef et al., 2009; 2010b).
Category: