1. J. E. Mayer and M. G. Mayer,Statistical Mechanics, 2nd ed., (John Wiley, New York, 1977), Chap. 7.
2. P. R. Bunker,Molecular Symmetry and Spectroscopy, (Academic, New York, 1979), Chap. 8.
3. A. O. Caride and S. I. Zanette,J. Chem. Phys. 76:1179 (1982).