1. : Williams' Obstetrics, ed 14. New York, Appleton-Century-Crofts, 1971, p 680.
2. FETAL MALFORMATIONS AND ABNORMALITIES
3. : Ultrasonography in Obstetrics and Gynecology. Baltimore, Williams & Wilkins, 1977, p. 77.
4. : Ultrasonography in Obstetrics and Gynecology. New York, Appleton-Century-Crofts, 1977, p 156.
5. Ultrasound in the diagnosis of congenital anomalies