1. Solitons, edited by R.K. Bullough, P.J. Caudrey, (Springer-Verlag, Berlin, 1980); R.K. Dodd, J.C. Eilbeck, H.C. Morris, Solitons and Nonlinear Equations (Academic Press, London, 1984); P.G. Drazin, R.S. Johnson, Solitons: An Introduction (Cambridge University Press, Cambridge, 1988); C.H. Gu, Soliton Theory and Its Applications (Springer-Verlag, New York, 1995); E. Infeld, G. Rowlands, Nonlinear Waves, Solitons, and Chaos, 2nd edn. (Cambridge University Press, Cambridge, 2000); C. Rogers, W.K. Schief, Bäcklund and Darboux Transformations, Geometry and Modern Applications in Soliton Theory, Cambridge Texts in Applied Mathematics, (Cambridge University Press, Cambridge, 2002)
2. S.Y. Lou, J. Phys. A: Math. Gen. 36, 3877 (2003)
3. X.Y. Tang, S.Y. Lou, J. Math. Phys. 44, 4000 (2003)
4. C.L. Bai, H. Zhao, Z. Naturfursch A 59, 412 (2004)
5. C.L. Bai, H. Zhao, Chaos Soliton and Fractals 23, 777 (2005); C.L. Bai, H. Zhao, Eur. Phys. J. B 42, 581 (2004)