@article{SM_2013_204_11_a1,
     author = {A. A. Borisenko and K. D. Drach},
     title = {Closeness to spheres of hypersurfaces with normal curvature bounded below},
     journal = {Sbornik. Mathematics},
     pages = {1565--1583},
     year = {2013},
     volume = {204},
     number = {11},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_2013_204_11_a1/}
}