@article{DAN_1986_287_3_a0,
     author = {A. A. Agrachev and R. V. Gamkrelidze},
     title = {Morse and {Maslov} indices for the extremals of controllable},
     journal = {Doklady Akademii Nauk},
     pages = {521--524},
     publisher = {mathdoc},
     volume = {287},
     number = {3},
     year = {1986},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1986_287_3_a0/}
}