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:We then apply PVI to three probabilistic models: the Dirichlet process mixture model (DPMM; Antoniak, 1974; Escobar and West, 1995; Fearnhead, 2004), the infinite HMM (iHMM; Beal et al., 2002; Teh et al., 2006), and the Ising model.
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