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:FISH was carried out according to Pinkel et al. (1986)
using 5S rDNA probes obtained by PCR from Prochilodus genomic DNA using the primers A (5_-TACGCCCGATCTCG TCCGATC-3_) and B (5_-CAGGCTGGTATGGCCGTAAGC-3_) (Pendás et al., 1994).
Category: