1. L. Pauling,Z. Phys. 48, 344 (1926).
2. References are given in L. Pauling and E. B. Wilson, Jr.,Introduction to Quantum Mechanics (McGraw-Hill, New York, 1935), and L. Pauling,The Nature of the Chemical Bond (Cornell University Press, Ithaca, New York, 1960), 3rd edn.
3. W. D. Harkins,J. Am. Chem. Soc. 42, 1956 (1920).
4. L. Pauling,Science 150, 297 (1965).
5. R. K. Nesbet,Phys. Rev. 100, 228 (1955).