1. I. T. Kiguradze and T. A. Chanturiya, Asymptotic Properties of the Solutions of Nonautonomous Ordinary Differential Equations [in Russian], Nauka, Moscow (1990).
2. V. M. Evtukhov and Mousa Jaber Abu Elshour, “Asymptotic behavior of solutions of second-order nonlinear differential equations close to linear equations,” Mem. Different. Equat. Math. Phys., 43, 97–106 (2008).
3. Mousa Jaber Abu-Elshour, “Asymptotics of solutions of nonautonomous second-order ordinary differential equations close to linear equations,” Nelin. Kolyvannya, 11, No. 2, 230–241 (2008); English translation: Nonlin. Oscillations, 11, No. 2, 242–254 (2008).
4. Mousa Jaber Abu Elshour, “Asymptotic representations of the solutions of a class of the second-order nonautonomous differential equations,” Mem. Different. Equat. Math. Phys., 44, 59–68 (2008).
5. Mousa Jaber Abu Elshour and V. M. Evtukhov, “Asymptotic representations for solutions of a class of second-order nonlinear differential equations,” Miscolc Math. Notes, 2, 119–127 (2009).