@article{DE_1983_19_2_a7,
     author = {E. L. Tonkov},
     title = {The controllability set of a linear equation},
     journal = {Differencialʹnye uravneni\^a},
     pages = {269--278},
     publisher = {mathdoc},
     volume = {19},
     number = {2},
     year = {1983},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1983_19_2_a7/}
}