%0 Journal Article %A A. A. Zaitsev %T Variational method of calculating the partition functions of the lattice-gas and Ising models %J Teoretičeskaâ i matematičeskaâ fizika %D 1989 %P 437-445 %V 79 %N 3 %U http://geodesic.mathdoc.fr/item/TMF_1989_79_3_a11/ %G ru %F TMF_1989_79_3_a11