1. P. M. Morse, Phys. Rev. 34, 57 (1929).PHRVAO0031-899X
2. M. A. Pariseau, I. Suzuki, and J. Overend, J. Chem. Phys. 42, 2335 (1965).JCPSA60021-9606
3. J. A. Aldous and I. M. Mills, Spectrochim. Acta 19, 1567 (1963).SPACA50038-6987
4. J. W. Russell, C. D. Needham, and J. Overend, J. Chem. Phys. 45, 3383 (1966).JCPSA60021-9606
5. The force constants Kii etc., are defined in Ref. 2.