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@article{MAN_1956__132_160513, author = {F. Stummel}, title = {Singul\"are elliptische {Differentialoperatoren} in {Hilbertschen} {R\"aumen.}}, journal = {Mathematische Annalen}, pages = {150--176}, publisher = {mathdoc}, volume = {132}, year = {1956}, zbl = {0070.34603}, url = {http://geodesic.mathdoc.fr/item/MAN_1956__132_160513/} }
F. Stummel. Singuläre elliptische Differentialoperatoren in Hilbertschen Räumen.. Mathematische Annalen, Tome 132 (1956), pp. 150-176. http://geodesic.mathdoc.fr/item/MAN_1956__132_160513/