@article{MM2_1972__7_154120,
     author = {Klaus Kalb},
     title = {Spektrale {Invarianz} bei verallgemeinerten {Eigenfunktionsentwicklungen.}},
     journal = {Manuscripta mathematica},
     pages = {271--298},
     publisher = {mathdoc},
     volume = {7},
     year = {1972},
     zbl = {0245.47022},
     url = {http://geodesic.mathdoc.fr/item/MM2_1972__7_154120/}
}