On the theory of upper and lower solutions and the solvability of quasilinear integro-differential equations

In this paper nonlinear integro-differential equations of the type $\partial u/\partial t-\Delta u=\Phi(x,t,u,F(u))$ are considered, where $F(u)$ is a nonlinear integral operator.
The concepts of upper and lower solutions of problems for nonlinear integro-differential equations are defined, and based on this new solvability criteria for these problems are obtained. Nonstationary, as well as stationary, integro-differential equations are considered.
Bibliography: 10 titles.