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:In phase III studies, nivolumab has demonstrated an overall survival (OS) benefit in squamous NSCLC (9), nonsquamous NSCLC (10), melanoma (11), RCC (12), and squamous cell carcinoma of the head and neck (13), and is being developed for several other tumor types.
Category: