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:58% of ethnically matched control chromosomes.(8) Examination of the dbSNP shows that the frequency of the rs6746030 polymorphism in control samples is ethnicity dependent: American Caucasians of European descent, 12.
Category: