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:To infer the most likely number of groups (K) we compared the log probability LnP(D) of different values for K using an ad hoc statistic (DK, [26]) that calculates the second order rate of change of LnP(D).
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