1. L. D. Landau and E. M. Lifshitz, Course of Theoretical Physics, Vol. 8: Electrodynamics of Continuous Media (Nauka, Moscow, 1982; Pergamon, New York, 1984).
2. A. I. Akhiezer, V. G. Bar’yakhtar, and S. V. Peletminskii, Spin Waves (North-Holland, Amsterdam, 1968; Nauka, Moscow, 1967).
3. A. F. Andreev and V. I. Marchenko, Sov. Phys. Usp. 23, 21 (1980).
4. A. M. Perelomov, Sov. Phys. Usp. 20, 703 (1977).
5. A. F. Andreev and I. A. Grishchuk, Sov. Phys. JETP 60, 267 (1984).