1. R. V. Pound, in Mössbauer Spectroscopy II, Ed. by U. Gonser (Springer, Berlin, 1981), p. 31.
2. Yu. A. Il’inskii and R. V. Khokhlov, Sov. Phys. JETP 38, 809 (1973).
3. V. I. Gol’danskii, S. V. Karyagin, and V. A. Namiot, JETP Lett. 19, 324 (1974).
4. Yu. M. Kagan, JETP Lett. 19, 373 (1974).
5. A. V. Andreev, Yu. A. Il’inskii, and R. V. Khokhlov, Sov. Phys. JETP 40, 819 (1974).