1. S. P. Novikov, S. V. Manakov, L. P. Pitaevskii, and V. E. Zakharov, Theory of Solitons: the Inverse Scattering Method (Nauka, Moscow, 1980; Consultants Bureau, New York, 1984).
2. A. I. Maimistov and A. M. Basharov, Nonlinear Optical Waves (Kluwer, Dordrecht, 1999).
3. D. J. Kaup, Stud. Appl. Math. 31, 121 (1976).
4. V. I. Karpman and E. M. Maslov, Zh. Éksp. Teor. Fiz. 73, 537 (1977) [Sov. Phys. JETP 46, 281 (1977)].
5. Yu. S. Kivshar and B. A. Malomed, Rev. Mod. Phys. 61, 763 (1989).