@article{MZ_1966__94_170631,
     author = {Heinz-Dieter Niessen},
     title = {Algebraische {Untersuchungen} \"uber separierbare {Operatoren.}},
     journal = {Mathematische Zeitschrift},
     pages = {328--348},
     publisher = {mathdoc},
     volume = {94},
     year = {1966},
     zbl = {0149.07603},
     url = {http://geodesic.mathdoc.fr/item/MZ_1966__94_170631/}
}