@article{VMUMM_1985_1_a10,
     author = {\`E. R. Rozendorn},
     title = {Some class of surfaces of negative curvature with singularities on lines},
     journal = {Vestnik Moskovskogo universiteta. Matematika, mehanika},
     pages = {50--52},
     publisher = {mathdoc},
     number = {1},
     year = {1985},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VMUMM_1985_1_a10/}
}