@article{DE_1995_31_6_a6,
     author = {N. N. Petrov},
     title = {On a problem in {sub-Riemannian} geometry},
     journal = {Differencialʹnye uravneni\^a},
     pages = {973--979},
     publisher = {mathdoc},
     volume = {31},
     number = {6},
     year = {1995},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1995_31_6_a6/}
}