@article{VMUMM_1994_2_a13,
     author = {\`E. R. Rozendorn},
     title = {The exactness of theorems on the smoothness of a surface with negative curvature of given smoothness},
     journal = {Vestnik Moskovskogo universiteta. Matematika, mehanika},
     pages = {99--101},
     publisher = {mathdoc},
     number = {2},
     year = {1994},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VMUMM_1994_2_a13/}
}