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2. P.G. de Gennes, J. Prost, The Physics of Liquid Crystals, 2nd edn. (Clarendon Press, Oxford, 1993), p. 408, Chap. 8
3. S. Singh, Liquid Crystals Fundamentals (World Scientific, Singapore, 2002), p. 221, Chap. 6
4. S. Kumar (ed.), Liquid Crystals in the Nineties and Beyond (World Scientific, Singapore, 1995)
5. P. Oswald, P. Pieranski, Smectic and Columnar Liquid Crystals: Concepts and Physical Properties Illustrated by Experiments (Taylor and Francis, London, 2006)