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:These clusters of informative voxels, along with a cluster implicating the occipital cortex, have also been consistently found in neuroimaging studies using statistical parametric mapping (Bush et al., 2000; Colibazzi et al., 2010; Gerber et al., 2008; Hagan et al., 2009; Killgore and Yurgelun-Todd, 2004; Narumoto et al., 2001; Posner et al., 2009; Robins et al., 2009; Wager et al., 2008).
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