@article{DE_1975_11_7_a6,
     author = {S. Yu. Kultyshev and E. L. Tonkov},
     title = {Controllability of a linear nonstationary system},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1206--1216},
     publisher = {mathdoc},
     volume = {11},
     number = {7},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1975_11_7_a6/}
}