1. P. G. de Gennes and J. Prost, The Physics of Liquid Crystals (Clarendon, Oxford, 1994).
2. M. Kleman, Points, Lines and Walls in Liquid Crystals, Magnetic Systems and Various Ordered Media (Wiley, Chichester, 1983).
3. Defects in Liquid Crystals: Computer Simulations, Theory and Experiments, Ed. by O. D. Lavrentovich, P. Pasini, S. Zannoni, and S. Zumer (Kluwer, Dordrecht, 2001).
4. M. V. Kurik and O. D. Lavrentovich, Sov. Phys. Usp. 31, 196 (1988).
5. P. V. Dolganov, V. M. Zhilin, V. K. Dolganov, and E. I. Kats, JETP Lett. 89, 161 (2009).