@article{DAN_1991_320_2_a8,
     author = {M. M. Khapaev},
     title = {Conditions for the controllability of singularly perturbed systems},
     journal = {Doklady Akademii Nauk},
     pages = {300--302},
     publisher = {mathdoc},
     volume = {320},
     number = {2},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1991_320_2_a8/}
}