@article{DAN_1991_316_2_a7,
     author = {A. V. Pogorelov},
     title = {On a theorem of {Beltrami}},
     journal = {Doklady Akademii Nauk},
     pages = {297--299},
     publisher = {mathdoc},
     volume = {316},
     number = {2},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1991_316_2_a7/}
}