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:Two types of purposeful sampling were used to recruit ten participants from physiotherapy [1], occupational therapy [1], kinesiology [1], cognitive behavioural therapy [2], medicine [1], psychology [1], return to work [1], resource specialty [1], and customer service [1].
Category: