1. V. M. Evtukhov, Asymptotic Representations of the Solutions of Nonautonomous Ordinary Differential Equations [in Russian], Doctoral-Degree Thesis (Physics and Mathematics), Kiev (1998).
2. V. M. Evtukhov and E. S. Vladova, "Asymptotic representations of solutions of essentially nonlinear cyclic systems of ordinary differential equations," Differents. Uravn., 48, No. 5, 622-639 (2012)
3. English translation: Differ. Equat., 48, No. 5, 630-646 (2012).
4. V. M. Evtukhov and L. A. Kirillova, "On the asymptotics of solutions of nonlinear second-order differential equations," Differents. Uravn., 41, No. 8, 1053-1061 (2005)
5. English translation: Differ. Equat., 41, No. 8, 1105-1114 (2005).