@article{DE_1985_21_12_a5,
     author = {N. N. Petrov},
     title = {The minimum number of vector fields forming a control system with given properties},
     journal = {Differencialʹnye uravneni\^a},
     pages = {2063--2068},
     publisher = {mathdoc},
     volume = {21},
     number = {12},
     year = {1985},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1985_21_12_a5/}
}