Metformin versus ethinyl estradiol-cyproterone acetate in the treatment of nonobese women with polycystic ovary syndrome: a randomized study - Morin-Papunen, L; Vauhkonen, I; Koivunen, R; Ruokonen, A; Martikainen, H; Tapanainen, J S (J Clin Endocrinol Metab, 2003)