1. H. Haken, Phys. Lett. 53A, 77 (1975).
2. see e.g. A. N. Oraevsky, Molekulyarnye Generatory (molecular-beam masers) (Nauk., Moscow, 1964 );
3. Ya. I. Khanin, Dinamika Kvantovykh Generatorov (Dynamics of Quantum Generators) (Sov. Radio, Moscow, 1975 )
4. see e.g. the special issues of J. Opt. Soc. Am. B2 (1985) and B5 (1988).
5. I. Burak, P.L. Houston, D.G. Sutton and J.I. Steinfeld, IEEE J. Quant. Electron. QE-7, 73 (1971);