1. Yu. L. Klimontovich, A. S. Kovalev, and P. S. Landa, ?Natural fluctuations in lasers,? Usp. Fiz. Nauk,106, 279?313 (1972).
2. S. I. Bychkov, D. P. Luk'yanov, and A. I. Bakalyar, Laser Gyroscope [in Russian], Sov. Radio, Moscow (1975).
3. S. G. Zeiger, Yu. L. Klimontovich, P. S. Landa, et al., Wave and Fluctuation Processes in Lasers [in Russian], Nauka, Moscow (1974), pp. 377?379.
4. G. S. Kruglik, Quantum Statistical Theory of Ring Lasers [in Russian], Nauka i Tekhnika, Minsk (1978), pp. 58?82.
5. T. Sakurai, T. Ohta, and T. Ogawa, ?Unsaturated gain and output power of a 6328 Å He-Ne gas laser,? IEEE J. Quantum Electron.,QE-4, 65?70 (1968).