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@article{DAN_1966_170_6_a0, author = {I. V. Gel'man}, title = {Stability of normally solvable extensions of partial differential operators}, journal = {Doklady Akademii Nauk}, pages = {1239--1242}, publisher = {mathdoc}, volume = {170}, number = {6}, year = {1966}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DAN_1966_170_6_a0/} }
I. V. Gel'man. Stability of normally solvable extensions of partial differential operators. Doklady Akademii Nauk, Tome 170 (1966) no. 6, pp. 1239-1242. http://geodesic.mathdoc.fr/item/DAN_1966_170_6_a0/