@article{DAN_1972_207_2_a11,
     author = {\`E. R. Rozendorn},
     title = {Some sufficient conditions for regularity of a surface with constant negative intrinsic curvature},
     journal = {Doklady Akademii Nauk},
     pages = {296--299},
     publisher = {mathdoc},
     volume = {207},
     number = {2},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1972_207_2_a11/}
}