@article{ELMA_1969__24_140929,
     author = {H.-J. Kanold},
     title = {\"Uber },
     journal = {Elemente der Mathematik},
     pages = {61--62},
     publisher = {mathdoc},
     volume = {24},
     year = {1969},
     zbl = {0174.33702},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1969__24_140929/}
}