1. D. Ruelle, Statistical Mechanics, New York (1969).
2. N. N. Bogolyubov and B. I. Khatset, Dokl. Akad. Nauk SSSR,66, 321 (1949).
3. G. P. Egorychev, Integral Representation and Calculation of Combinatorial Sums [in Russian], Nauka, Novosibirsk (1977), p. 286.
4. Ya. G. Sinai, Theory of Phase Transitions [in Russian], Nauka, Moscow (1980), p. 208.
5. R. A. Minlos and Ya. G. Sinai, Tr. Mosk. Matem. Ob-va,17, 213 (1967).