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:lalandi transcriptome sequences (YTK002, YTK008, YTK011, YTK017 and YTK019) [3] and three loci (Sdu21, Sdu32 and Sdu46) validated from the literature [18, 19] were used to genotype the experiment fish for parentage analysis in this study.
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