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:Clinically, they usually present with unilateral nasal obstruction, but other symptoms have also been reported such as epistaxis, purulent rhinorrhoea, postnasal drip, snoring, obstructive sleep apnoea, dysphonia, and dysphagia [3, 12].
Category: