@article{FAA_1989_23_3_a20,
     author = {V. D. Sedykh},
     title = {An infinitely smooth compact convex hypersurface with a shadow whose boundary is not twice-differentiable},
     journal = {Funkcionalʹnyj analiz i ego prilo\v{z}eni\^a},
     pages = {86--87},
     publisher = {mathdoc},
     volume = {23},
     number = {3},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/FAA_1989_23_3_a20/}
}