1. E. Wolf: in theProc. of the Symp. on Opt. Masers (New York, 1963), p. 29.
2. R. J. Glauber:Phys. Rev.,130, 2529 (1963).
3. See for example,M. Born andE. Wolf:Principles of Optics, 3rd edition, Chapter X (Oxford, 1965).
4. U. M. Titulaer andR. J. Glauber:Phys. Rev.,140, B 676 (1965).
5. E. C. G. Sudarshan:Phys. Rev., Lett.,10, 277 (1963).