@article{SM_1970_11_2_a9,
     author = {A. S. Vinogradskii},
     title = {Boundary properties of surfaces with slowly varying negative curvature},
     journal = {Sbornik. Mathematics},
     pages = {257--271},
     publisher = {mathdoc},
     volume = {11},
     number = {2},
     year = {1970},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1970_11_2_a9/}
}