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@article{DE_1967_3_5_a1, author = {V. A. Pliss}, title = {Recurrent motions of periodic systems of two differential equations}, journal = {Differencialʹnye uravneni\^a}, pages = {722--732}, publisher = {mathdoc}, volume = {3}, number = {5}, year = {1967}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1967_3_5_a1/} }
V. A. Pliss. Recurrent motions of periodic systems of two differential equations. Differencialʹnye uravneniâ, Tome 3 (1967) no. 5, pp. 722-732. http://geodesic.mathdoc.fr/item/DE_1967_3_5_a1/