RT Journal Article SR Electronic T1 Association of estrogen and progestin potency of oral contraceptives with ovarian carcinoma risk JF Journal of Family Planning and Reproductive Health Care JO J Fam Plann Reprod Health Care FD British Medical Journal Publishing Group SP 154 OP 154 DO 10.1783/147118907781004732 VO 33 IS 3 A1 Maybin, Jackie YR 2007 UL http://jfprhc.bmj.com/content/33/3/154.2.abstract AB