It gives a scheme for solving mixed boundary value problems of elasticity theory in an endless belt in the form of explicit expansions Feature-Fadl Papkovich (homogeneous solutions of elasticity theory). On each side of the strip has at one point changing types of boundary conditions, and these points lie on a line perpendicular to the axis of the strip. Mixed boundary problems are among the most complicated (think for bodies with cracks). At the same time, the distribution pattern of stresses and strains in the vicinity of the boundary conditions change in such points is of greatest practical interest, for example in problems of mechanical reliability of thin elements aircraft panels. Driving solutions initially understands the simple example of a mixed boundary value problem for harmonic operator in an infinite strip.