Determining amounts of gases and liquids with throttle devices

A. Sh. Kiyasbeili et al., Frequency-Time Ultrasonic Flow-Meters and Counters [in Russian], Mashinostroenie, Moscow (1984). L. I. Zhuravlev et al., Inventor's Certificate No. 614328, Byull. Izobret., No. 25 (1978). Yu. A. Bogomolov et al., Inventor's Certificate No. 800652, Byull. Izobret., No. 4 (1981). G. I. Birger and N. I. Brazhnikov, Ultrasonic Flow-Meters [in Russian], Mashinostroenie, Moscow (1964). A. G. Ovchinnikov, Inventor's Certificate No. 1206618, Byull. Izobret., No. 3 (1986).