1. V. D. Pustovitov and V. D. Shafranov, in Reviews of Plasma Physics, Ed. by B. B. Kadomtsev (Energoatomizdat, Moscow, 1987; Consultants Bureau, New York, 1990), Vol. 15.
2. A. H. Boozer, Rev. Mod. Phys. 23, 1071 (2005).
3. A. H. Boozer, Phys. Fluids 26, 1288 (1983).
4. V. I. Ilgisonis and A. A. Skovoroda, Zh. Eksp. Teor. Fiz. 137, 1018 (2010) [JETP 110, 890 (2010)].
5. R. Z. Sagdeev, D. A. Usikov, and G. M. Zaslavsky, Nonlinear Physics (Nauka, Moscow, 1988; Harwood Academic, New York, 1988).