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:They are scale-free, i.e., there are many nodes with few neighbors and few nodes with many neighbors, which are called hubs (Barabási et al 2011; Pavlopoulos
Communicated by: Ron AWevers
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10545-018-0140-0)…
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