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2. L. D. Landau and E. M. Lifshitz, Course of Theoretical Physics, Vol. 7: Theory of Elasticity (Nauka, Moscow, 1987; Pergamon, New York, 1984).
3. L. M. Brekhovskikh, Waves in Layered Media (Nauka, Moscow, 1973; Academic, New York, 1980).
4. V. I. Alshits and J. Lothe, Wave Motion 3, 297 (1981).
5. J. Lothe and L. Wang, Wave Motion 21, 163 (1995).