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:qRT-PCR of androgen regulated genes (TMPRSS2, KLK3), and DNA repair genes (PRKDC, POLE2, FANCI), were carried out as described previously (4) using the following primer pairs: GAPDH (F: GGAGCGAGATCCCTCCAAAAT, R: GGCTGTTGTCATACTTCTCATGG); TMPRSS2 (F: TACTCTGGAAGTTCATGGGC R: GTCATCCACTATTCCTTGGCT); KLK3 (F: TGAACCAGAGGAGTTCTTGAC R: TGACGTGATACCTTGAAGCA); PRKDC (F: AGCTGGCTTGCGCCTATTT R: GGGCACACCACTTTAACAAGA); POLE2 (F: CTGCTCCGTGGTGAAGCTAT, R: ATTCCTGGACTGCTGCTTCC); FANCI (F: TTCTCACTGCTCTTTTCAGGGAT, R: GCCCTGTTTCCTTTAGCTGC).
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