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:Previous studies have suggested recording electrograms over at least 5 s to increase the accuracy of fractionation and DF assessment.(6,7) For the purpose of this study, we assessed degree of fractionation as a continuous variable by CFE-mean analysis to include all data between the range of 40 and 300 ms so as to include as wide a range of AF electrograms as possible.
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