1. For more detailed discussions of the points brought up in the present note, see J. C. Slater and J. H. Wood, Statistical Exchange and the Total Energy of a Crystal, Preprint No. 191, Quantum Theory Project, University of Florida, Gainesville, Florida 32601, to be published in International Journal of Quantum Chemistry, Symposium No. 4, January, 1971. See also J. C. Slater and J. H. Wood, Optical Transitions and the Statistical Exchange in Crystals, Phys. Rev. (to be published), and J. C, Slater, Transition Probabilities and Fractional Occupation Numbers in Atoms, to be published in volume honoring E. U. Condon,
2. R. Gaspar, Über eine Approximation des Hartree-Fockschen Potentials durch eine universelle Potentialfunktion, Acta Phys. Hung. 3, 263 (1954).
3. W. Kohn and L. J. Sham, Self-Consistent Equations Including Exchange and Correlation Effects, Phys. Rev. 140, A1133 (1965).
4. J. C. Slater, J. B. Mann, T. M. Wilson, and J. H. Wood, Non-Integral Occupation Numbers in Transition Atoms, Phys. Rev. 184, 672 (1969).
5. J. Frenkel, On the Transformation of Light into Heat in Solids, Phys. Rev. 37, 17 (1931).