1. A. B. Migdal, Qualitative Methods in Quantum Theory (Nauka, Moscow, 1975; Benjamin, Reading, 1977).
2. L. D. Landau and E. M. Lifshitz, Quantum Mechanics: Non-Relativistic Theory (Nauka, Moscow, 1974; Pergamon, Oxford, 1977).
3. N. Fröman and P. O. Fröman, JWKB Approximation: Contributions to the Theory (North-Holland, Amsterdam, 1965; Mir, Moscow, 1967).
4. J. Heading, An Introduction to Phase-Integral Methods (Wiley, New York, 1962; Mir, Moscow, 1965).
5. L. I. Schiff, Quantum Mechanics (McGraw-Hill, New York, 1955; Inostrannaya Literatura, Moscow, 1957).