@article{DAN_1970_193_2_a13,
     author = {V. S. Fedii},
     title = {Estimates in the $H_{(s)}$ norms, and hypoellipticity},
     journal = {Doklady Akademii Nauk},
     pages = {301--303},
     publisher = {mathdoc},
     volume = {193},
     number = {2},
     year = {1970},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1970_193_2_a13/}
}