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@article{DE_1977_13_5_a1, author = {N. I. Vulpe and K. S. Sibirskii}, title = {Geometric classification of a quadratic differential system}, journal = {Differencialʹnye uravneni\^a}, pages = {803--814}, publisher = {mathdoc}, volume = {13}, number = {5}, year = {1977}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1977_13_5_a1/} }
N. I. Vulpe; K. S. Sibirskii. Geometric classification of a quadratic differential system. Differencialʹnye uravneniâ, Tome 13 (1977) no. 5, pp. 803-814. http://geodesic.mathdoc.fr/item/DE_1977_13_5_a1/