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2. F. C. Frank, “On the Theory of Liquid Crystals,” Disc. Faraday Soc., 25, p. 19 (1958).
3. P. Sheng, “Introduction to the Elastic Continuum Theory of Liquid Crystals,” Chapter 8.
4. P. deGennes, The Physics of Liquid Crystals, Oxford University Press, London (1974).
5. W. Helfrich, “Electric Alignment of Liquid Crystals,” Mol. Cryst. and Liq. Cryst., 21, p. 187 (1973).