@article{DAN_1975_224_2_a3,
     author = {V. I. Burenkov},
     title = {On the extension of functions with preservation and with deterioration of the differential properties},
     journal = {Doklady Akademii Nauk},
     pages = {269--272},
     publisher = {mathdoc},
     volume = {224},
     number = {2},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1975_224_2_a3/}
}