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 reference methods we considered in the com-
parative study include the following:
• Hierarchical Dirichlet process, denoted as HDP (Goldwater et al., 2009);
• Nested Pitman-Yor process, denoted as NPY (Mochihashi et al., 2009);
• Adaptor grammars, denoted as AG (Johnson and Goldwater, 2009);
• Branching entropy + MDL, denoted as EntMDL (Zhikov et al., 2010);
• Bootstrap voting experts + MDL, denoted as BVE-MDL (Hewlett and Cohen, 2011);
• Description length gain, denoted as DLG (Zhao and Kit, 2008).
Category: