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@article{DE_1968_4_6_a20, author = {P. S. Belevets}, title = {A certain class of dynamical systems with two closed algebraic trajectories}, journal = {Differencialʹnye uravneni\^a}, pages = {1150--1153}, publisher = {mathdoc}, volume = {4}, number = {6}, year = {1968}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1968_4_6_a20/} }
P. S. Belevets. A certain class of dynamical systems with two closed algebraic trajectories. Differencialʹnye uravneniâ, Tome 4 (1968) no. 6, pp. 1150-1153. http://geodesic.mathdoc.fr/item/DE_1968_4_6_a20/