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 4-year survival of 73% in the AFB/MEVP cohort compares favorably with the long-term survival reported by other centers of excellence.(29,30) Perhaps more importantly, however, the long-term survival demonstrated with the use of AFB/MEVP equates the long-term survival reported by our group after open repair of standard infrarenal aortic aneurysms.
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