1. |
V. V. Basov, A. V. Zefirov, “Generalized normal forms of the systems of ordinary differential equations with a quasi-homogeneous polynomial $(\alpha x_1^2+x_2, x_1 x_2)$ in the unperturbed part”, Vestnik of Saint Petersburg University. Mathematics. Mechanics. Astronomy, 8:1 (2021), 12–28 ; Vestn. St. Petersbg. Univ., Math., 8:3 (2021), 8–21 |