@article{DE_1991_27_12_a31,
     author = {A. A. Liverovskiy and N. N. Petrov},
     title = {Letter to the editors: {``Some} differential-topological problems in control theory''},
     journal = {Differencialʹnye uravneni\^a},
     pages = {2201},
     publisher = {mathdoc},
     volume = {27},
     number = {12},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1991_27_12_a31/}
}