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 stability of these societies depends on individuals’ decisions governing group membership, which are intimately related to individuals’ costs and benefits of living in the group (Danchin and Wagner 1997; Clutton-Brock et al. 1998; Buston 2003a).
Category: