@article{MZM_1973_13_6_a9,
     author = {Yu. D. Burago and V. A. Toponogov},
     title = {On three-dimensional {Riemannian} spaces with curvature bounded above},
     journal = {Matemati\v{c}eskie zametki},
     pages = {881--887},
     publisher = {mathdoc},
     volume = {13},
     number = {6},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1973_13_6_a9/}
}