1. Solitons, Nonlinear Evolution Equations and Inverse Scattering, Vol. 149;Ablowitz,1991
2. G.L. Lamb Jr., Elements of Soliton Theory, New York, 1980, p. 29.
3. Solitons and the Inverse Scattering Transform;Ablowitz,1981
4. Exact theory of two-dimensional self-focusing and one-dimensional self-modulation of waves in nonlinear media;Shabat;Sov. Phys. JETP,1972
5. Stability of periodic waves of finite amplitude on the surface of a deep fluid;Zakharov;J. Appl. Mech. Tech. Phy.,1968