1. Yu. S. Kuz’minov, Electro-Optical and Nonlinear Optical Lithium Niobate Crystal (Nauka, Moscow, 1987) [in Russian].
2. V. A. Maksimenko, A. V. Syu>i, and Yu. M. Karpets, Photoinduced Processes in Lithium Niobate Crystals (FIZMATLIT, Moscow, 2008) [in Russian].
3. N. V. Sidorov, T. R. Volk, B. N. Mavrin, and V. T. Kalinnikov, Lithium Niobate: Defects, Photorefraction, Vibrational Spectrum, Polaritons (Nauka, Moscow, 2003) [in Russian].
4. M. Goulkov, M. Imlau, and M. Woleke, Phys. Rev. B 77, 235 110 (2008).
5. E. Kratzig and O. Schirmer, Appl. Phys. 62, 131 (1989).