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:Among the 28 patients, the clinical details and follow-up information were provided for 25 patients [4,5,14,15], 18 of whom underwent surgery and were free from the disease without postoperative radioiodine ablation therapy.
Category: