@article{MZ_1976__149_172398,
     author = {Gerhard Freiling},
     title = {Nichtselbstadjungierte {Differentialoperatoren} im nichtkompakten {Fall.}},
     journal = {Mathematische Zeitschrift},
     pages = {267--280},
     publisher = {mathdoc},
     volume = {149},
     year = {1976},
     zbl = {0316.34023},
     url = {http://geodesic.mathdoc.fr/item/MZ_1976__149_172398/}
}