G Schreckenbach and T Ziegler, Int. J. Quantum Chem. 60, 753 (1996)
G Schreckenbach and T Ziegler, Int. J. Quantum Chem. 61, 899 (1997)
S K Wolff and T Ziegler, J. Chem. Phys. 109, 895 (1998)
S K Wolff, T Ziegler, E van Lenthe, and E J Baerends, J. Chem.
Phys. 110, 7689 (1999)