1. N. E. Mal’tsev and S. D. Chuprov, Dokl. Akad. Nauk SSSR 275(2), 475 (1981) [Sov. Phys. Dokl., No. 2 (1981)].
2. V. A. Baranov and V. S. Grigor’ev, Akust. Zh. 28, 588 (1982) [Sov. Phys. Acoust. 28, 349 (1982)].
3. I. G. Malkina and V. P. Shevtsov, Akust. Zh. 35, 870 (1989) [Sov. Phys. Acoust. 35, 506 (1989)].
4. I. G. Malkina and V. P. Shevtsov, Akust. Zh. 36, 319 (1990) [Sov. Phys. Acoust. 36, 173 (1990)].
5. V. N. Lobanov and Yu. V. Petukhov, Akust. Zh. 39, 1093 (1993) [Acoust. Phys. 39, 574 (1993)].