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:In Wales (15) there were nonsignificantly higher levels of plasma androstenedione in cases than in controls; in South African blacks (18) cases had significantly lower levels than controls and in Finland ( 17) cases and controls had similar levels.
Category: