1. S. A. Akhmanov, V. A. Vysloukh, and A. S. Chirkin,Optics of Femtosecond Laser Pulses [in Russian], Nauka, Moscow (1988).
2. V. I. Bespalov, A. G. Litvak, and V. I. Talanov, in:Nonlinear Optics [in Russian], Nauka, Novosibirsk (1968), p. 428.
3. V. E. Zakharov, S. V. Manakov, S. P. Novikov, L. P. Pitaevskii, in:Theory of Solitons (Method of the Inverse Problem) (S. P. Novikov, ed.) [in Russian], Nauka, Moscow (1980).
4. J. Satsuma and N. YajimaSuppl. Progr. Theor. Phys., No. 55, 284 (1974).
5. M. J. Ablovitz and H. Segur, in:Solitons and the Method of the Inverse Problem (V. E. Zakharov, ed.) [Russian translation], Mir, Moscow (1987).