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 use of MRI helps with this challenge when planning a bone tumor resection [28, 30, 31] as it allows the surgeon to determine the extent of the tumor and its relationship to surrounding structures, which can be correlated to intraoperative landmarks [23] to estimate the location of the tumor and the osteotomies required to resect it.
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