@article{DE_1989_25_6_a4,
     author = {G. S. Osipenko},
     title = {Examples of perturbations of invariant manifolds},
     journal = {Differencialʹnye uravneni\^a},
     pages = {943--950},
     publisher = {mathdoc},
     volume = {25},
     number = {6},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1989_25_6_a4/}
}