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:…a high overlap between PSD-95 and PLCb1 signals in the cerebral cortex, thus confirming a well defined subcellular location for PLCb1, which previously could be only demonstrated by Western blot analysis of subcellular fractions (Taguchi et al., 2007) or electron microscopy (Fukaya et al., 2008).
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