A prospective study on the effects on hemostasis of two oral contraceptives containing drospirenone in combination with either 30 or 20 microg ethinyl estradiol and a reference containing desogestrel and 30 microg ethinyl estradiol - Kluft, C; Endrikat, J; Mulder, S M; Gerlinger, C; Heithecker, R (Contraception, 2006)