1. L. M. Lyamshev and N. S. Shevyakhov, Akust. Zh. 19, 918 (1973) [Sov. Phys. Acoust. 19, 592 (1973)].
2. M. K. Balakirev and I. A. Gilinskii, Fiz. Tverd. Tela 16, 3144 (1974) [Sov. Phys. Solid State 16, 2038 (1974)].
3. Yu. V. Gulyaev and V. P. Plesskii, Pis’ma Zh. Tekh. Fiz. 3, 1028 (1977) [Sov. Tech. Phys. Lett. 3, 422 (1977)].
4. M. K. Balakirev and A. V. Gorchakov, in Proceedings of the 10th All-Union Conference on Quantum Acoustics and Acoustoelectronics (FAN, Tashkent, 1978), p. 76.
5. L. M. Lyamshev and N. S. Shevyakhov, Akust. Zh. 32, 198 (1986) [Sov. Phys. Acoust. 32, 117 (1986)].