References
- Bernstine R. L., Callagan D. A. Ultrasonic doppler inspection of the fetal heart. Amer J Obstet Gynec 1966; 95: 1001
- Johnson W. L., Stegall H. F., Lein J. N., Rushmer R. F. Detection of fetal life in early pregnancy with an ultrasonic Doppler flowmeter. Obstet Gynec 1965; 26: 305
- Jouppila P. Ultrasound in the diagnosis of early pregnancy and its complications. Acta Obstet Gynec Scand 1971; 50(Suppl. 15)
- Kratochwil A., Eisenhut L. Der frïheste Nachweis der fetalen Herzaktion durch Ultraschall. Geburtsh Frauenheilk 1967; 27: 176
- Kuah K. B., Embrey M. P. Experiences with an ultrasonic foetal pulse detector. Brit Med J 1968; 1: 438
- Robinson H. P. Detection of fetal heart movement in first trimester of pregnancy using pulsed ultrasound. Brit Med J 1972; 4: 466
- Robinson H. P. 1973, Personal communications