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:DiVerent studies on SVCT2 in mouse, rat and human cells have shown either a single immunoreactive band of 50,000 Da (Li et al. 2003; Godoy et al. 2007; Savini et al. 2007a) or a 65,000–75,000 Da doublet, possibly due to glycosylation (Garcia Mde et al. 2005; Savini et al. 2007b).
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