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:Performance evaluation
 The performance of developed models was evaluated by calculating overall accuracy of prediction, sensitivity, specificity (Han et al., 2008; Lamanna et al., 2008) and Matthews correlation coefficient (MCC) (Matthews, 1975).
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