@article{DE_1972_8_12_a3,
     author = {V. I. Blagodatskikh},
     title = {The convexity of spheres of attainability},
     journal = {Differencialʹnye uravneni\^a},
     pages = {2149--2155},
     publisher = {mathdoc},
     volume = {8},
     number = {12},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1972_8_12_a3/}
}