1. Craig, D. P.: Proc. roy. Soc. A, 202, 498 (1950).
2. Cram, D. J.: Record Chem. Progr. 20, 71 (1959).
3. Daudel, R., R. Lefebvre and C. Moser: Quantum Chemistry, Methods and Applications. New York: Interscience 1959.
4. Davydov, A. S.: J. Exptl. theoret. Physics 18, 210 (1948).
5. De Voe, H., and I. Tinoco, Jr.: private communication.