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:Although diversity exists between species and the sexes, EDHF makes a large contribution to endothelium-dependent vasodilatation in various vascular beds in men and nonpregnant women (3, 7, 21, 24, 25, 30, 31).
Category: