1. The Quantum Theory of Optical Coherence
2. H.M. Nussenzveig, Introduction to Quantum Optics, Gordon and Breach, New York, 1972, p. 73.
3. C. Cohen-Tannoudji, J. Du Pont-Roc, G. Grinberg, Photons and Atoms, Wiley, New York, 1989, p. 217.
4. L. Mandel, E. Wolf, Optical Coherence and Quantum Optics, Cambridge University Press, Cambridge, 1995, p. 568.
5. W.H. Louisell, Quantum Statistical Properties of Radiation, Wiley, New York, 1973, p. 231.