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:Moreover, canids are the only known eutherian mammals to carry a Prdm9 which has acquired disruptive mutations (Mu~noz-Fuentes et al. 2011; Ponting 2011; Axelsson et al. 2012) (a marsupial, the opossum Monodelphis domestica, has a Prdm9 which lacks zinc fingers; Ponting 2011).
Category: