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:Another common characteristic of co-authorship networks is the existence of community or cluster structure (Girvan and Newman 2002; Newman 2004a; Leskovec et al. 2009; Savić et al. 2015) where clusters are viewed as subsets of nodes that are more densely internally connected than with the rest of…
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