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:Only some forms of agriculture have the potential to be both productive in terms of human food resources and conservation ‘friendly’: one such form of land use is livestock farming on natural pastures (O’Connor 2005; Little et al. 2013).
Category: