Each transformation introduces at least one additional zero so that at least two subgraphs are joined and the number of subgraphs is reduced by at least one at each step. Starting with a reduced matrix and with n < m, it is seen at once that there can not be more than n linear subgraphs. With reduced grouped matrices, the number is usually much less than this. Then the reduction to two complementary subgraphs can be made in no more than n - 2 transformations, once the matrix is reduced. With the informal version, the number of linear subgraphs once the reduced grouped matrices have been further reduced with the use of transformations eliminating surplus assignments, is usually very small.