@article{SM_1972_18_1_a3,
     author = {Z. D. Usmanov},
     title = {On~a~problem concerning the deformation of a~surface with a~flat point},
     journal = {Sbornik. Mathematics},
     pages = {61--81},
     publisher = {mathdoc},
     volume = {18},
     number = {1},
     year = {1972},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1972_18_1_a3/}
}