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@article{DE_1973_9_6_a20, author = {A. V. Osipov}, title = {On the question of the existence of a transformation to normal form}, journal = {Differencialʹnye uravneni\^a}, pages = {1149--1150}, publisher = {mathdoc}, volume = {9}, number = {6}, year = {1973}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1973_9_6_a20/} }
A. V. Osipov. On the question of the existence of a transformation to normal form. Differencialʹnye uravneniâ, Tome 9 (1973) no. 6, pp. 1149-1150. http://geodesic.mathdoc.fr/item/DE_1973_9_6_a20/