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:…isoforms (N-ter, R-233, PLCb136–87, D-8) recognized two bands with apparent molecular masses consistent with previous reports (Lee et al., 1987, 1993; Fukaya et al., 2008), whereas G-12 antibody only detected the heaviest band, in agreement with its expected specificity for the PLCb1a isoform (Fig.
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