1. G. A. Askar’yan, Sov. Phys. JETP 15, 1088 (1962).
2. V. I. Talanov, Izv. Vyssh. Uchebn. Zaved., Radiofiz. 7, 564 (1964).
3. S. A. Akhmanov, A. P. Sukhorukov, and R. V. Khokhlov, Sov. Phys.—Usp. 10(5), 609 (1967).
4. V. N. Lugovoi and A. M. Prokhorov, Sov. Phys.—Usp. 16(5), 658 (1973).
5. S. N. Vlasov and V. I. Talanov, Wave Self-Focusing (Institute of Applied Physics, Russian Academy of Sciences, Nizhni Novgorod, 1997) [in Russian].