1. S. A, Agafonov, “Stability of nonconservative systems and an estimate for the attraction region,” Prikl. Mat. Mekh. 67, No. 2 (2003).
2. S. A. Agafonov, “On reducing nonautonomous systems to autonomous, and mechanical applications,” In:Voronezh Winter Mathematical School, “Contemporary Methods of Function Theory and Related Problems, January 27-February 4, 1999, Abstracts of Reports [in Russian ], Voronezh (1999),p.8.