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:In these species, even for purebred dogs, LD decay is rapid over less than 50 kb, and is very limited over 100 kb (Lindblad-Toh et al. 2005; Axelsson et al. 2012).
Category: