1. N. Bloembergen:Nonlinear Optics (Benjamin, New York 1977)
2. T.F. Heinz, C.K. Chen, D. Ricard, Y.R. Shen: Phys. Rev. Lett.48, 478 (1982)
3. G.A. Reider, A.J. Schmidt, G. Marowsky: Opt. Commun47, 223 (1983)
4. The dye laser FL 2000 was kindly left to our disposal by Dr. R. Vehrenkamp, Lambda Physik, Göttingen
5. M. Born, E. Wolf:Principles of Optics. 4th ed. (Pergamon Press, London 1970)