1. P.G. de Gennes, Mol. Cryst. Liq. Cryst. 12, 193 (1971).
2. A. Saupe, Z. Naturforsch. Teil A 19, 161 (1964).
3. G. Vertogen and W.H. de Jeu, Thermotropic Liquid Crystals, Fun damentals (Springer, New York, 1988).
4. W. Maier and A. Saupe, Z. Naturforsch. Teil A 14, 882 (1959); 15, 287 (1960).
5. P.L. Nordio and U. Segre, The Molecular Physics of Liquid Crystals, edited by G.R. Luckhurst and G.W. Gray (Academic, London, 1979), Chap. 19.