Footnotes
1. Leidenberger FA. Klinische Endokrinologie fur Frauenärzte. Berlin, Germany: Springer Verlag, 1998
2. Baltzer J, Mickan H. Gynäkologie: Ein kurzgefaßtes Lehrbuch/Kern. Neubearbeitete Auflage. Stuttgart, Germany, Georg Thieme Verlag, 1985
3. Organon. NuvaRing (etonogestrel/ethinyl estradiol vaginal ring) 2001. Available at: http://www.epigee.org/guide/inserts/nuvaring.pdf. (Accessed 5 October 2003)
4. Ortho-McNeil Pharmceutical Inc. Ortho Evra (Norelgestromin/ Ethinyl estradiol transdermal system) 2001. Available at: http://www.ortho.mcneil.com/products/pi/pdfs/orthoevra.pdf. (Accessed 5 October 2003)
5. Ortho-McNeil Pharmaceutical Inc. Ortho Tri-Cyclen Lo tablets (norgestimate/ethinyl estradiol) 2002. Available at: http://www.ortho-mcneil.com/products/pi/pdfs/orthtricyclenlo.pdf (Accessed 5 October 2003)
6. Speroff L, Darney PD. Periodic Abstinence. A clinical guide for contraception. 3rd edn. Philadelphia, PA: Lippincott Williams and Wilkins, 2001