@article{DAN_1990_311_2_a0,
     author = {A. A. Agrachev and R. V. Gamkrelidze},
     title = {The ``time substitution'' variation in optimal control},
     journal = {Doklady Akademii Nauk},
     pages = {265--270},
     publisher = {mathdoc},
     volume = {311},
     number = {2},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1990_311_2_a0/}
}