1. R. J. Glauber:Phys. Lett.,21, 650 (1966).
2. See, for example,W. H. Louisell:Radiation and Noise in Quantum Electronics (New York, 1964).
3. R. J. Glauber:Phys. Rev. Lett.,10, 84 (1963);Phys. Rev.,131, 2766 (1963);E. C. G. Sudarshan:Phys. Rev. Lett,10, 277 (1963).
4. See, for example, the lectures ofF. T. Arecchi andH. A. Haus:Quantum optics, inProceedings of the International School of Physics, Enrico Fermi, Course XLII, edited byR. J. Glauber (New York, 1969).
5. D. Holliday andA. E. Glassgold:Phys. Rev.,139 A, 1717 (1965).