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:Cases were identified and clinical data collected through the Genetic Studies of Human Developmental Disorders at the Medical College of Wisconsin, Milwaukee, WI or the A/M Clinical Registry at the Albert Einstein Medical Center, Philadelphia, PA.
Genomic DNA was extracted using the Autopure LS system (Qiagen, Valencia, CA) from blood or buccal samples and the SOX2 coding region was amplified using primers: set 1 forward, 5'-AGT CCC GGC CGG GCC GAG-3', and set 1 reverse, 5'-GGT AGC CCA GCT GGT CCT G-3', and set 2 forward, 5'-CAA GAC GCT CAT GAA GAA GG-3', and set 2 reverse, 5'-TAC TCT CCT CTT TTG CAC CC-3'.
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