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:Related work in this stream conceptualizes the factors that make some services more amenable for offshore BPO (Apte and Mason 1995; Mithas and Whitaker 2005; Venkatraman 2004), and examines supplier capabilities, best practices, and lessons from BPO using case-based research (Cullen et al. 2005; Feeny et al. 2005; Lacity et al. 2003).
Category: