Hemostatic and metabolic effects of lowering the ethinyl-estradiol dose from 30 μg to 20 μg in oral contraceptives containing desogestrel - Basdevant, A; Conard, J; Pelissier, C; Guyene, TT; Lapousterle, C; Mayer, M; Gran, BG; Degrelle, H (Contraception, 1993)