@article{MZ_1970__117_171414,
     author = {Helmut H. Schaefer},
     title = {Topologische {Nilpotenz} irreduzibler {Operatoren.}},
     journal = {Mathematische Zeitschrift},
     pages = {135--140},
     year = {1970},
     volume = {117},
     zbl = {0246.47001},
     url = {http://geodesic.mathdoc.fr/item/MZ_1970__117_171414/}
}