@article{DE_1973_9_11_a23,
     author = {N. N. Petrov},
     title = {Certain invariant sets of control systems},
     journal = {Differencialʹnye uravneni\^a},
     pages = {2095--2096},
     publisher = {mathdoc},
     volume = {9},
     number = {11},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1973_9_11_a23/}
}