M. P. SPENCER, “Cardiovascular diagnosis with frequency spectral analysis (FSA) and continuous wave doppler (CWD)”, Arch. Acoust., vol. 9, no. 1-2, pp. 181–190, Jul. 2015, Accessed: Jan. 17, 2026. [Online]. Available: https://acoustics.ippt.gov.pl/index.php/aa/article/view/3211