1. H. Haken, H. Risken, and W. Weidlich: Z. Physik 206, 355 (1967)
2. H. Haken: Handbuch der Physik, Vol. XXV/2c, ed. by L. Genzel ( Springer-Verlag, Berlin, 1970 ) pp. 64–65
3. W. H. Louisell: Quantum Statistical Properties of Radiation ( Wiley, New York, 1973 ) pp. 375–390
4. C. W. Gardiner: Handbook of Stochastic Methods for Physics, Chemistry and the Natural Sciences (Springer-Verlag, Berlin, 1983) pp. 78, 79, 402
5. A. Einstein: Phys. Z. 18, 121 (1917)