@article{DAN_1973_211_1_a13,
     author = {M. M. Khrustalev},
     title = {Necessary and sufficient conditions for an optimal control problem},
     journal = {Doklady Akademii Nauk},
     pages = {59--62},
     publisher = {mathdoc},
     volume = {211},
     number = {1},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1973_211_1_a13/}
}