1. American College of Obstetricians and Gynecologists: Diagnostic Ultrasound in Obstetrics and Gynecology. ACOG Technical Bulletin 63, 1981.
2. American Institute of Ultrasound in Medicine: Antepartum Obstetrical Ultrasound Examination Guidelines, 1985.
3. ACOG Technical Bulletin # 116, Ultrasound in Pregnancy, 1988.