1. S. A. Akhmanov and R. V. Khokhlov, ?New developments in nonlinear optics,? Usp. Fiz. Nauk,95, No. 1, 231?247 (1968).
2. G. A. Askar'yan, ?Action of the gradient of the field on an intense electromagnetic beam on electrons and atoms,? Zh. Éksp. i Teor. Fiz.,42, No. 6, 1567 (1962).
3. L. A. Ostrovskii, ?Electromagnetic waves in nonlinear media with dispersion,? Zh. Tekh. Fiz.,33, No. 8, 905 (1963).
4. G. B. Whitham, ?Nonlinear dispersive waves,? Proc. Roy. Soc.,283 A, No. 1393, 238 (1965).
5. A. G. Litvak, ?Self-focusing of electromagnetic waves in a plasma,? Izv. VUZ. Radiofiz.,9, No. 5, 900 (1965).