@article{MT_1987_9_a1,
     author = {S. A. Akbarov and V. A. Toponogov},
     title = {A theorem on the congruence of the angles of a triangle for a class of {Riemannian} manifolds},
     journal = {Matemati\v{c}eskie trudy},
     pages = {16--25},
     year = {1987},
     volume = {9},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MT_1987_9_a1/}
}