The sparsity of the CI Hamiltonian Matrix is demonstrated for a few sample molecules in figure . The larger the CI Hamiltonian Matrix is the greater the sparsity, also many nonzero elements, although not exactly zero are approximately-zero. These approximately-zero elements are due to the sparsity of the SO-matrices (from the electron-repulsion). We notice however, that in all cases, the matrices are diagonally dominant, indicative that Slater-Condon Rule 0 is usually the dominant source of nonzero elements.