1. C.H. Townes (Ed.), Quantum Electronics, Columbia University Press, New York, 1960.
2. J.R. Singer (Ed.), Advances in Quantum Electronics, Columbia University Press, New York, 1961.
3. A.L. Schawlow, Advances in Quantum Electronics, Columbia University Press, New York, 1961, p. 50.
4. Personal discussion with the author, 1962.
5. The Effect of Temperature upon the Absorption Spectrum of a Synthetic Ruby