“…Elliptic systems of di erential equations are of crucial importance in modelization and description of a wide variety of phenomena such as uid dynamics, quantum physics, sound, heat, electrostatics, di usion, gravitation, chemistry, biology, simulation of airplane, calculator charts, and time prediction. PDEs are equations involving functions of several variables and their derivatives and model multidimensional systems generalizing ODEs (ordinary di erential equations), which deal with functions of a single variable and their derivatives (see, for example, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]).…”