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@article{DE_1970_6_10_a2, author = {N. F. Otrokov}, title = {Conditions for the existence of a loop of a separatrix}, journal = {Differencialʹnye uravneni\^a}, pages = {1761--1771}, publisher = {mathdoc}, volume = {6}, number = {10}, year = {1970}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1970_6_10_a2/} }
N. F. Otrokov. Conditions for the existence of a loop of a separatrix. Differencialʹnye uravneniâ, Tome 6 (1970) no. 10, pp. 1761-1771. http://geodesic.mathdoc.fr/item/DE_1970_6_10_a2/