1. Yu. L. Klimontovich (editor), Wave and Fluctuation Processes in Lasers [in Russian], Nauka, Moscow (1974).
2. F. Aronowitz, Phys. Rev.,139, A635 (1965).
3. G. S. Kruglik, Theory of Pulsations in an Annular Laser [in Russian], Nauka i Tekhnika, Minsk (1967).
4. M. I. Burnashev and V. E. Privalov, Kvantovaya Elektron.,3, 2581 (1976).
5. L. A. Mel'nikov, Radiotekh. Elektron.,23, 366 (1978).