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@article{DE_1991_27_8_a0, author = {V. V. Amel'kin}, title = {Classification of limit cycles}, journal = {Differencialʹnye uravneni\^a}, pages = {1291--1296}, publisher = {mathdoc}, volume = {27}, number = {8}, year = {1991}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1991_27_8_a0/} }
V. V. Amel'kin. Classification of limit cycles. Differencialʹnye uravneniâ, Tome 27 (1991) no. 8, pp. 1291-1296. http://geodesic.mathdoc.fr/item/DE_1991_27_8_a0/