1. R.P. Feynman and A.R. Hibbs, Quantum mechanics and path integrals, Mc Graw-Hill, New York (1965)
2. See for a review: F.W. Wiegel, Path integral methods in statistical mechanics. Phys. Reports 16C, 57 (1975).
3. N. N. Bogoliubov and D.U. Shirkov, Introduction to the theory of quantized fields. Interscience Publ. New York (1959).
4. R.L. Stratonovich, Dok1. Akad. nauk. SSSR 115 (1957). Translated Sov. Phys. Dok l. 2 416 (1958);
5. J. Hubbard, Phys. Rev. Lett. 3, 77 (1959).