Numerical solution of second order elliptical equations with mixed derivatives by effective iterative methods

The second order elliptical equations with mixed derivatives are considered. These problems appear in the medium with different properties in some directions. Discret model has got on the base of central-difference approximations. Spectra of matrices are presented and properties of these spectra are investigated. New two-step skew-symmetric iterative method is used for the solution of linear system of algebraic equations.