1. A. A. Mazannikov, V. V. Tyutekin, and M. V. Fedoryuk, Akust. Zh. 26, 759 (1980) [Sov. Phys. Acoust. 26, 428 (1980)].
2. P. A. Nelson, A. R. D. Curtis, S. J. Elliot, and A. J. Bullmore, J. Sound Vibr. 117(1), 1 (1987).
3. G. V. Alekseev and E. G. Komarov, Mat. Model. 3(12), 52 (1991).
4. G. V. Alekseev and E. G. Komarov, Akust. Zh. 39, 5 (1993) [Acoust. Phys. 39, 1 (1993)].
5. G. V. Alekseev and E. G. Komarov, J. Inv. Ill-Posed Probl. 2(2), 85 (1994).