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@article{DE_1989_25_12_a9, author = {V. I. Mironenko}, title = {Simple systems and periodic solutions of differential equations}, journal = {Differencialʹnye uravneni\^a}, pages = {2109--2114}, publisher = {mathdoc}, volume = {25}, number = {12}, year = {1989}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1989_25_12_a9/} }
V. I. Mironenko. Simple systems and periodic solutions of differential equations. Differencialʹnye uravneniâ, Tome 25 (1989) no. 12, pp. 2109-2114. http://geodesic.mathdoc.fr/item/DE_1989_25_12_a9/