T. GUDRA, “Analysis of a resonator with a directional ultrasonic vibration converter of R-L type using the finite elements method”, Arch. Acoust., vol. 25, no. 2, pp. 157–174, Jan. 2000, Accessed: Apr. 26, 2025. [Online]. Available: https://acoustics3.ippt.pan.pl/index.php/aa/article/view/361