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@article{DE_1969_5_5_a20, author = {V. I. Chemodanov}, title = {Isochronism in the case of a focus}, journal = {Differencialʹnye uravneni\^a}, pages = {964--966}, publisher = {mathdoc}, volume = {5}, number = {5}, year = {1969}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1969_5_5_a20/} }
V. I. Chemodanov. Isochronism in the case of a focus. Differencialʹnye uravneniâ, Tome 5 (1969) no. 5, pp. 964-966. http://geodesic.mathdoc.fr/item/DE_1969_5_5_a20/