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2. See for example Photorefractive Materials and Their Applications I & II, edited by P. Günter and J.-P. Huignard (Springer Verlag, Berlin, Germany, 1988).
3. S. Ducharme, J. C. Scott, R. J. Twieg, and W. E. Moerner, Postdeadline Paper, Optical Society of America Annual Meeting, (Boston, MA, November 5-9, 1990).
4. S. Ducharme, J. C. Scott, R. J. Twieg, and W. E. Moerner, Phys. Rev. Lett. 66, 1846 (1991).
5. P. Günter, Phys. Rep. 93, 199 (1982).