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@article{DE_1967_3_5_a7, author = {L. A. Cherkas}, title = {Perturbations of a differential equation}, journal = {Differencialʹnye uravneni\^a}, pages = {781--786}, publisher = {mathdoc}, volume = {3}, number = {5}, year = {1967}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1967_3_5_a7/} }
L. A. Cherkas. Perturbations of a differential equation. Differencialʹnye uravneniâ, Tome 3 (1967) no. 5, pp. 781-786. http://geodesic.mathdoc.fr/item/DE_1967_3_5_a7/