1. Shen, Y. R. 1984.The Principles of Non-linear Optics, 187–190. John Wiley and Sons. Chap. 11, Chap. 3, p. 42–44, 47–50, Chap. 14, p. 24z, Chap. 17, p. 330
2. Arakelyan, S. M. and Chilingaryan, Yu. S. 1984.Non-linear Optics of Liquid Crystals, 163–178. Nauka. (in Russian), Chap. 4