“…To solve the system of equations (1.12), (1.13) for / = I,...,/, where / is the total number of the grid nodes, we applied an iterative method, which is similar to the Schwarz alternation method (see, for example, [12,[14][15][16][17][23][24][25][26]). The method used can be viewed as a block Gauss-Seidel method with convergence acceleration of iterations [21,22].…”