%0 Journal Article %A A. A. Gainetdinova %A R. K. Gazizov %T Integration of systems of two second-order ordinary differential equations with a small parameter that admit four essential operators %J Sibirskie èlektronnye matematičeskie izvestiâ %D 2020 %P 604-614 %V 17 %I mathdoc %U http://geodesic.mathdoc.fr/item/SEMR_2020_17_a90/ %G en %F SEMR_2020_17_a90