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:The receiver operator characteristic (ROC) curve shows the tradeoff between sensitivity and specificity as one changes the cut-off values for positivity.(9,10) The sensitivity versus 1-specificity plot in ROC space is called ROC curve.
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