1. X.D. Yang, A. Joets, R. Ribotta, p. 194 in Propagation in Systems far from equilibrium, J.E. Wesfreid, H.R. Brand, P. Manneville, G. Albinet, N. Boccara Eds., Springer Series in Synergetics, Springer-Verlag, Berlin (1988).
2. E. Dubois-Violette, P.G. de Gennes, O. Parodi, J. Phys. (Paris) 32, 305 (1971);
3. P.G. de Gennes, “The Physics of Liquid Crystals”, Clarendon, Oxford (1974).
4. A. Joets and R. Ribotta, Phys. Rev. Lett. 60, 2164 (1988);
5. also in “Propagation in Systems far from Equilibrium” J.E. Wesfreid, H.R. Brand, P. Manneville, G. Albinet and N. Boccara eds., Springer, Berlin (1988); and in the Proceedings of the 12th International Liquid Crystals Conference, Aug. 1988, Freiburg), Liquid Crystals, London (1988).