@article{DE_1973_9_3_a21,
     author = {V. A. Dobrynskii and A. N. Sharkovskii},
     title = {Orbit stability of trajectories},
     journal = {Differencialʹnye uravneni\^a},
     pages = {558--559},
     year = {1973},
     volume = {9},
     number = {3},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1973_9_3_a21/}
}