“…The quantities u g j , U f + l , j , u%, uZm+ 1, i = 0, 1 ,..., n + 1, j = 0, 1, ..., rn +1, CY = 1,2 are assumed to be known. Let us consider two schemes for (15): a certain alternating direction scheme and the completely implicit scheme in which all the terms in the right-hand side of (15) are taken from the upper time layer. The first scheme is economical, but one cannot answer the question both on its monotony or even on its stability.…”