1. See, for instance, F. T. Arechi, E. O. Schulz-Dubois (eds.): Laser Handbook, Vol. 1 (North-Holland, Amsterdam 1972);
2. M. Sargent III, M. O. Scully, W. E. Lamb Jr.: Laser Physics (Addison-Wesley, Reading, MA 1974);
3. O. Svelto: Principles of Lasers, 2nd ed. (Plenum, New York 1982);
4. H. Haken: Laser Theory (Springer, Berlin, Heidelberg 1984)
5. D. B. Brayton: Appl. Opt. 13, 2346 (1974)