@article{MZ_1967__97_170712,
     author = {Friedrich Stummel},
     title = {Elliptische {Differenzoperatoren} unter {Dirichletrandbedingungen.}},
     journal = {Mathematische Zeitschrift},
     pages = {169--211},
     publisher = {mathdoc},
     volume = {97},
     year = {1967},
     url = {http://geodesic.mathdoc.fr/item/MZ_1967__97_170712/}
}