1. L. D. Landau and E. M. Lifshits, Course of Theoretical Physics. Vol. 5: Statistical Physics [in Russian], GITTL, Moscow, 1951; English transl.: Pergamon Press, Oxford, 1968.
2. R. P. Feynman and A. R. Hibbs, Quantum Mechanics and Path Integrals, McGraw-Hill, New York, 1965.
3. V. P. Maslov, Perturbation Theory and Asymptotic Methods [in Russian], Izdat. Moskov. Univ., Moscow, 1965; French transl.: Dunod, Paris, 1972.
4. V. P. Maslov, Asymptotic Methods and Perturbation Theory [in Russian], Nauka, Moscow, 1988.
5. V. I. Arnold, Mathematical Methods of Classical Mechanics [in Russian], Nauka, Moscow, 1989; English transl.: Springer-Verlag, New York, 1989.