1. M. Born andE. Wolf:Principles of Optics (New York, 1959).
2. Proc. of the III Intern. Symp. on Quantum Electr. (Paris, 1963).
3. D. Mandel in (2), p. 101.
4. Proc. Symp. on Optical Masers (New York, 1963).
5. J. P. Goldsborough:Appl. Opt.,3, 267 (1964).