1. see for instance Y.R. Shen, Principles of Nonlinear Optics, John Wiley, New-York, 1984
2. see for instance, Nonlinear Optics : Materials and Devices. Eds C. Flytzanis and J.L. Oudar, Springer Verlag, Berlin, 1986
3. see for instance G. Fowles, Introduction to Modern Optics, Holt Rinehart and Winston, New York, 1975
4. A. Nussbaum and R. Phillips, Comtemporarv Optics for Scientists and Engineers, Prentice-Hall New York, 1976
5. K. Kubota, J. Phys.Soc.Jap.,29, 998 (1970)