Most of the information on this site came from the following sources:

• ACOG Committee on Practice Bulletins. ACOG Practice Bulletin. 2000;
  15:1-9.
  
  
• The American Heritage Stedman’s Medical Dictionary. Boston, MA: Houghton Mifflin Company; 1995.
  
  
• Berek JS, Adashi EY, Hillard PA, eds. Novak’s Gynecology. 12th ed. Baltimore, MD: Lippincott Williams & Wilkins; 1996.
  
  
• Committee on Gynecologic Practice. ACOG committee opinion premenstrual syndrome. Int J Gynaecol Obstet. 1995;50:80-84.
  
  
• Danforth’s Obstetrics and Gynecology. 9th ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2003.
  
  
• Dorland’s Illustrated Medical Dictionary. 30th ed. Philadelphia, PA: Elsevier; 2003.
  
  
• Mishell DR, Strauss JF III, Barbieri RL, eds. Contraception. In: Yen and Jaffe's Reproductive Endocrinology: Physiology, Pathophysiology, and Clinical Management. 5th ed. Philadelphia, PA: Elsevier; 2004.
  
  
• Nakajima ST. Contemporary Guide to Contraception. 1st ed. Newtown, PA: Handbooks in Health Care Co; 2005.
  
  
• Rebar RW, Erickson GF. Menstrual cycle and fertility. In: Goldman L, Ausiello D, eds. Cecil Textbook of Medicine. 22nd ed, Philadelphia, PA: Saunders; 2004:1495-1509.
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• Speroff L, Fritz MA. Clinical Gynecologic Endocrinology and Infertility. 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2005.
  
  
• Starr C, McMillan B. The female reproductive system. In: Human Biology. 6th ed. Pacific Grove, CA: Brooks/Cole; 2005.