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:The mtDNA and NRY variation in Brazilian admixed populations was first mined from the literature: Afro-Brazilian mtDNA [34–36] (n = 277) and NRY [12,34,35] (n = 380) and White Brazilian mtDNA [11,12] (n = 247) and NRY [12] (n = 180) and mtDNA/ NRY n = 245/132 of the general population of Cuba [37].
Category: