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:These included the fatigue severity scale (FSS) [5], the multidimensional fatigue inventory (MFI) [6], the Epworth Sleepiness Scale (ESS) [7], Parkinson’s Disease Sleep Scale (PDSS) [8], Beck Depression Inventory (BDI), the Visual Analog Mood Scale (VAMS) and the Short Form 36 (SF-36) [9] scale.
Category: