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:Multiple origins of geometrid female flightlessness (even within a single subfamily) were shown by molecular phylogenetic studies, based on the premise of unlikely events of reversal (Snäll et al. 2007; Wahlberg et al. 2010).
Category: