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:RNA was reverse-transcribed as described previously (Thalor et al., 2012), and the resultant cDNA was used for reverse transcriptionpolymerase chain reaction (RT-PCR) and quantitative RT-PCR (qRT-PCR) analyses (Sagor et al., 2013) with the primers listed in Table S1.
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