@article{MZ_1965__89_170449,
     author = {Birgitta Hellwig},
     title = {Ein {Kriterium} f\"ur die {Selbstadjungiertheit} singul\"orer elliptischer {Differentialoperatoren} im {Gebiet} {G.}},
     journal = {Mathematische Zeitschrift},
     pages = {333--344},
     publisher = {mathdoc},
     volume = {89},
     year = {1965},
     zbl = {0128.32902},
     url = {http://geodesic.mathdoc.fr/item/MZ_1965__89_170449/}
}