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:Measurement of the Tp-Te interval was obtained from leads V2 and V5, corrected for heart rate (cTp-Te).(11) The Tp-Te/QT and cTp-Te/QT ratios were calculated from these measurements.
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