1. N. V. Sidorov, T. R. Volk, B. N. Mavrin, and V. T. Kalinnikov, Lithium Niobate: Defects, Photorefraction, Vibrational Spectra, Polaritons [in Russian], Nauka, Moscow (2003).
2. T. Volk and M. Wohlecke, Lithium Niobate. Defects, Photorefraction and Ferroelectric Switching, Springer, Berlin (2008).
3. M. N. Palatnikov, N. V. Sidorov, O. V. Makarova, and I. V. Biryukova, Fundamental Aspects of Technology of Strongly Doped Crystals of Lithium Niobate [in Russian], Izd-vo KNTs RAN, Apatity (2017).
4. X. Yang, G. Xu, H. Li, J. Zhu, and X. Wang, Crys. Res. Technol., 31, No. 4, 521–525 (1996).
5. Xi-Qi Feng and B. Tang Tong, J. Phys.: Condens. Matter, 5, 2423–2430 (1993).