1. See, for example, (a) W. J. Hehre, L. Radom, P. v.R. Schleyer, and J. A. Pople, Ab Initio Molecular Orbital Theory, Wiley, N.Y., 1986.
2. H. F. Schaefer, The Electronic Structure of Atoms and Molecules, Addison-Wesley, Reading, MA, 1972.
3. J. Z. H. Zhang and W. H. Miller, Chem. Phys. Lett. 140, 329 (1987).
4. J. Chem. Phys. 88, 4549 (1988).
5. J. Z. H. Zhang, S. I. Chu, and W. H. Miller, J. Chem. Phys. 88, 6233 (1988).