@article{DAN_1981_258_2_a1,
     author = {V. N. Berestovskii},
     title = {On spaces with bounded curvature},
     journal = {Doklady Akademii Nauk},
     pages = {269--271},
     year = {1981},
     volume = {258},
     number = {2},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1981_258_2_a1/}
}