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@article{DE_1999_35_7_a0, author = {V. V. Amel'kin and K. M. Al-Haider}, title = {Strong isochronism of polynomial differential systems with a center}, journal = {Differencialʹnye uravneni\^a}, pages = {867--873}, publisher = {mathdoc}, volume = {35}, number = {7}, year = {1999}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1999_35_7_a0/} }
V. V. Amel'kin; K. M. Al-Haider. Strong isochronism of polynomial differential systems with a center. Differencialʹnye uravneniâ, Tome 35 (1999) no. 7, pp. 867-873. http://geodesic.mathdoc.fr/item/DE_1999_35_7_a0/