1. We found interesting historical material at Dr J Woo’s website on www.obgyn.net and in the autobiographical narrative of Don Baker (an American Doppler ultrasound engineer) on www.ob-ultrasound.net.
2. Zagzebski J. A. Essentials of ultrasound physics. St Louis (Missouri): Mosby, 1996.
3. Foley W. D. Color Doppler flow imaging. Boston: Andover Med Pub ; 1991.
4. Walshaw C., Jobson D. A. Mechanics of fluids. London: Longmans ; 1962.
5. Nichols W. W., O’Rourke M. McDonald’s blood flow in arteries, theoretical, experimental and clinical principles, 4th edition. London: Arnold ; 1998.