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:Pain Relief/Disability/QoL Improvement With the exception of the 2 NEJM RCTs and a smaller RCT that reported no benefit of VP versus SHAM [4, 5] or NSM [11, 12] the vast majority of prospective comparative studies (Tables 1 and 2) support the superiority of VAPs versus NSM [13–27], with only 1 newer study reporting better results from KP until the 1st postoperative month and then equivalence [28].
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