1. Thornton KL. Principles of ultrasound. J Reprod Med. 1992;37:27–32.
2. American Institute of Ultrasound in Medicine. Medical ultrasound safety. Lauren, MD: AIUM. 1994, reapproved 2002
3. Kieler H, Ahlsten G, Haglund B, Salvesen K, Axelsson O. Routine ultrasound screening in pregnancy and the children’s subsequent neurologic development. Obstet Gynecol. 1998;91:750–6.
4. American Institute of Ultrasound in Medicine. Guidelines for cleaning and preparing endocavitary ultrasound transducers between patients. Retrieved Sept 15, 2005
5. ACOG. Guidelines for women’s health care. 2nd ed. Washington, DC: ACOG; 2002. p. 90.