@article{DAN_1992_324_6_a5,
     author = {M. M. Khapaev},
     title = {Singular differential equations in control problems with},
     journal = {Doklady Akademii Nauk},
     pages = {1166--1168},
     publisher = {mathdoc},
     volume = {324},
     number = {6},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1992_324_6_a5/}
}