1. Monastyrskii, M.I.: Topology of Gauge Fields and Condensed Matter. Plenum, New York (1993)
2. Sadoc, J.F. ed: Geometry in Condensed Matter Physics. World Scientific (1990)
3. Dubrovin, B.A., Novikov, S.P., Fomenko, A.T.: Modern Geometry—Methods and Applications: The Geometry of Surfaces, Transformation Groups and Fields. Springer-Verlag, New York (1993)
4. Rajaraman, R.: Solitons and Instantons. North-Holland, Amsterdam (1982)
5. Osipov, V.A.: Phys. Lett. A 146, 67 (1990)