1. V. I. Minkin, B. Ya. Simkin, and R. M. Minaev, The Theory of the Structure of Molecules [in Russian], Vysshaya Shkola, Moscow (1979), p. 150.
2. R. J. Gillespie, Molecular Geometry, Van Nos Reinhold (1972).
3. A. A. Frost, J. Chem. Phys.,47, 3707 (1967).
4. A. A. Frost, J. Chem. Phys.,47, 3714 (1967).
5. A. A. Frost, J. Phys. Chem.,72, 1289 (1968).