The method of functionals in the quantum theory of fields / by Yu. V. Novozhilov and A.V. Tulub. With an introductory article, Equations with variational derivatives in problems of statistical physics and of quantum field theory, by N.N. Bogolyubov. Novozhilov, I͡U. V. (I͡Uriĭ Viktorovich) Tulub, A. V., author. Quantum field theory. Functional analysis. QC174.5 .N6 531.38 NOM Includes bibliography. New York : Gordon and Breach, c1961. c1961. 1961 Text viii, 79 p. : eng Russian tracts on advanced mathematics and physics ; v. 5 Russian tracts on advanced mathematics and physics ; v. 5.