Voir la notice de l'article provenant de la source Math-Net.Ru
@article{DAN_1963_148_6_a1, author = {V. V. Grushin}, title = {Extension of smoothness to solutions of differential equations of smooth type}, journal = {Doklady Akademii Nauk}, pages = {1241--1244}, publisher = {mathdoc}, volume = {148}, number = {6}, year = {1963}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DAN_1963_148_6_a1/} }
V. V. Grushin. Extension of smoothness to solutions of differential equations of smooth type. Doklady Akademii Nauk, Tome 148 (1963) no. 6, pp. 1241-1244. http://geodesic.mathdoc.fr/item/DAN_1963_148_6_a1/