1. L. D. Landau and E. M. Lifshits, Quantum Mechanics, Vol. 3 [in Russian], Fizmatlit, Moscow (1963).
2. A. S. Davydov, Quantum Mechanics [in Russian], BHV-Peterburg Publisher, Saint Petersburg (2011).
3. L. Shiff, Quantum Mechanics [in Russian], Inostrannaya Literatura, Moscow (1959).
4. W. Louisell, Radiation and Noise in Quantum Electronics, McGrow-Hill Book Company, New York (1964).
5. V. N. Strekalov, Fiz. Tverd. Tela, 15, No. 5, 1373–1377 (1973).