1. Oral contraceptives and cardiovascular disease;Stadel;N Engl J Med,1981
2. effects of lowering estrogen content;Böttiger;Lancet,1980
3. A prospective study of past use of oral contraceptive agents and risk of cardiovascular disease;Stampfer;N Engl J Med,1988
4. Oral contraceptives and nonfatal vascular disease;Porter;Obstet Gynecol 1985;66:1. 5. Thorogood M, Mann J, Murphy M, Vessey M. Is oral contraceptive use still associated with an increased risk of fatal myocardial infarction? Report of a case-control study. Br J Obstet Gynecol,1991
5. Venous thromboembolism in relation to oral contraceptive use;Helmrich;Obstet Gynecol,1987