@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/}
}