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:Similar figures were reported by other studies investigating the combinations of CE-US þ CT and CT þ MRI in the setting of 1- to 2-cm HCC nodules.(9,24) In the present study, regardless of the dual combination of dynamic contrast imaging technique applied, no more than 13% of grade I tumors 2 cm were correctly identified on radiological examination, compared with >50% for grade II and grade III tumors of similar size.
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