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:Axelsson et al. (2012) and Auton et al. (2013) obtained estimates of Ne for dogs that differed 4-fold, and Freedman et al. (2014) detected very large changes in effective population size since the time of domestication and in different wolf lineages.
Category: