1. L. Pauling and E. B. Wilson, Introduction to Quantum Mechanics, McGraw-Hill Book Company, New York (1935).
2. G. Placzek, Handbuch der Radiologie, Volume VI, Part 2, Leipzig, 1934, p. 205.
3. E. B. Wilson, J. C. Decius, and P. C. Cross, Molecular Vibrations, McGraw-Hill Book Company, New York, 1955.
4. R. W. Wood, Phys. Rev. 36: 1421 (1930).
5. L. A. Woodward and D. A. Long, Trans. Faraday Soc. 45: 1131 (1949).