1. G. A. Askar’yan, “Effect of the gradient of the field of a high-power electromagnetic beam on atoms and electrons,” J. Exp. Teor. Fiz. 42(6), 1567 (1962).
2. V. E. Zakharov and E. A. Kuznetsov, “”Solitons and collapses: Two evolution scenarios of nonlinear wave systems,” Phys.-Uspekhi 55(6), 535–556 (2012).
3. A. A. Manenkov, “Self-focusing of laser pulses: Current state and future prospects,” Phys.-Uspekhi 54(1), 100–104 (2011).
4. R. W. Boyd, S. G. Lukishova, and Y. R. Shen, Selffocusing: Past and Present (Springer Science, Business Media, LLC, 2009).
5. N. F. Pilipetskii and A. R. Rustamov, “Observation of selffocusing of light in liquids,” JETP Lett. 2(2), 55–57 (1965).