1. V. M. Danilov, Astron. Zh. 79, 986 (2002) [Astron. Rep. 46, 887 (2002)].
2. V. M. Danilov, Astron. Zh. 79, 492 (2002) [Astron. Rep. 46, 443 (2002)].
3. V. M. Danilov, Astron. Zh. 77, 345 (2000) [Astron. Rep. 44, 298 (2000)].
4. A. A. El-Zant, Astron. Astrophys. 326, 113 (1997).
5. G. M. Zaslavskii and R. Z. Sagdeev, Introduction to Nonlinear Fhysics: From the Pendulum to Turbulence and Chaos [in Russian] (Nauka, Moscow, 1988).