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:A recent qualitative study explored the views of individuals living with SCI towards the descriptive systems of six established instruments (15D, AQoL 8-dimension questionnaire (AQoL-8D) [28], EQ5D-5L [29], HUI, QWB-SA [30] and the SF-36v2 [31]) [32].
Category: