1. Anal atresia: A prenatal ultrasound diagnosis;Bean;J. Clin. Ultrasound,1978
2. Studies in prolonged pregnancy. III. Amniocentesis in prolonged pregnancy;Beischer;Am. J. Obstet. Gynecol.,1969
3. Berkowitz, R. L., and Hobbins, J. C.: Ultrasound in the obstetrical patient. In Alad-jem, S., and Vidyasagar* C. (eds.): Atlas of Perinatology. Philadelphia, W. B. Saunders Co., in press.
4. Early prenatal diagnosis of neural tube defects by ultrasound;Campbell;Clin. Ob stet. Gynecol.,1977
5. Ultrasound in the diagnosis of spina bifida;Campbell;Lancet,1975