1. J. Golub, Opt. Seft., 20, 1847–1849 (1995).
2. S. Klewitz, P. Leiderer, S. Herminghaus, and S. Sogomonion, Opt. Seft., 21, 248–250 (1996).
3. S. Klewitz, S. Sogemonion, M. Woerniv, and S. Herminghaus, Opt. Commun., 154, 186–190 (1998).
4. S. Sogemonion, G. Grigorian, and K. Grigorian, Opt. Commun., 152, 351–354 (1998).
5. L. Niggl and Max Maier, Opt. Seft., 22, 910 (1997); Opt. Commun., 154, 65–69 (1998).