1. V. I. Tatarskii, Zh. Eksperim. i Teor. Fiz.,56, 2106 (1969).
2. V. I. Klyatskin, Zh. Eksperim. i Teor. Fiz.,57, 952 (1969).
3. V. I. Klyatskin and V. I. Tatarskii, Zh. Eksperim. i Teor. Fiz.,58, No. 2 (1970).
4. L. S. Dolin, Izv. VUZ, Radiofiz.,11, No. 6, 840 (1968).
5. L. A. Chernov, Abstracts of Paper Read at the Sixth All-Union Acoustic Conference [in Russian] (1968).