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:[34] A prior episode of symptomatic demyelinating optic neuritis was diagnosed when there was a history of a subacute episode of visual blurring or visual loss associated with eye pain and when this event was confirmed by medical record review and subject interview.
Category: