1. Vilenkin, A., and Shellard, E. P. S. Cosmic Strings and Other Topological Defects (Cambridge University Press, Cambridge, 1994).
2. Hehl, F. W., von der Heyde, P., Kerlick, G. D., Nester, J. M. (1976). Rev. Mod. Phys.
15, 393.
3. Scherk, J. and Schwarz, J. H. (1974). Phys. Lett. B
52, 347.
4. De Villiers, J.-P., and Frolov, V. (1998). Phys. Rev. D
58, 105018.
5. Green, M. B., Schwarz, J. H., and Witten, E. Superstring Theory (Cambridge University Press, 1987).