1. V. I. Domarkas and R.-I. Kazhis, Defektoskopiya, No. 3, 80 (1971).
2. V. I. Domarkas and R.-I. Kazhis, Control-Measurement Piezoelectric Transformers (Mintis, Vil’nyus, 1974) [in Russian].
3. J. L. Emeterio, A. Ramos, P. T. Sanz, A. Ruiz, and A. Azbaid, Ultrasonics 42, 277 (2004).
4. B. N. Alekseev and D. B. Dianov, Akust. Zh. 20, 663 (1974).
5. M. B. Gitis and A. S. Khimunin, Akust. Zh. 34, 735 (1988).