El Mir, HassineAlshams, Abdulla Sulaiman2022-05-182022-05-182005455https://drepo.sdl.edu.sa/handle/20.500.14154/3794The interest within the theory of Riemann – Hilbert Boundary Value Problems for high order elliptic differential th equations and systems was revived in nineties of the 20 century. When the theory of analytic functions, harmonic functions and the theory of two-dimensional singular integral equations could be applied to investigate the solvability of high order elliptic differential equations and systems with boundary conditions are more general than these classical conditions of Dirichlet and Neumann. Mathematicians are very interested in this field because its applications101enThesis