1. S.S. Shaik, J. Am. Chem. Soc. 103, 3692 (1981).
2. R.B. Woodward and R. Hoffmann, The Conservation of Orbital Symmetry, Academic Press, New York, 1970.
3. A. Pross and S.S. Shaik, Acc. Chem. Res. 16, 363 (1983).
4. S.S. Shaik, Prog. Phys. Org. Chem. 15, 197 (1985).
5. A. Pross, Adv. Phys. Org. Chem. 21, 99 (1985).