“…Similarly to (7), we denote r = (r 0,1 , · · · , r 0,d1−1 , · · · , r d1−1,0 , · · · , r d1−1,d1−1 ) t and s = (s 0,1 , · · · , s 0,d2−1 , · · · , s d2−1,0 , · · · , s d2−1,d2−1 ) t , where t stands for transpose. Set T = (t ij ), where the entries t ij are given by the coefficients t lmkn , l, m = 0, · · · , d 1 − 1, k, n = 0, · · · , d 2 − 1, (l, m), (k, n) = (0, 0), with the first two indices lm associated with the array index i, and the last two indices kn with the column index j of T .…”