This book is dedicated to the 120th birth anniversary of the famous Georgian Academician Nikoloz Muskhelishvili. Works of academician N. Muskhelishvili had a great impact in the further development of the elasticity theory and deferential and integral equations of mathematical-physics. Works of N. Muskhelishvili represents a basis of the numerous scientific researches in number of fields, which are used in order to solve technical problems. In the represented book, the following problems are considered: non-classical mathematical models describing pollution transfer and diffusion of various mixtures in the water streams; a non-stationary magneto hydrodynamic flow of conducting fluid between two infinite rotating porous discs lying from each other at a distance-h and the problem of wave propagation in an orthotropic half-plane.