1. M J Ablowitz and P A Clarkson, Solitons, nonlinear ev olution equations and inv erse scattering transform (Cambridge University Press, Cambridge, 1990)
2. V O Vakhnenko, E J Parkes and A J Morrison, Chaos, Solitons and Fractals 17(4), 683 (2003)
3. R Hirota, Direct method of finding exact solutions of nonlinear evolution equations, in: Backlund transformations edited by R Bullough and P Caudrey (Springer, Berlin, 1980), p. 1157
4. W Malfliet and W Hereman, Phys. Scr. 54, 563 (1996)
5. A M Wazwaz, Int. J. Comput. Math. 82(2), 235 (2005)