@article{SM_1982_41_3_a3,
     author = {A. V. Sarychev},
     title = {The index of the second variation of a~control system},
     journal = {Sbornik. Mathematics},
     pages = {383--401},
     publisher = {mathdoc},
     volume = {41},
     number = {3},
     year = {1982},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1982_41_3_a3/}
}