@article{ELMA_1962__17_140750,
     author = {J.J. Sch\"affer},
     title = {Ungel\"oste {Probleme.}},
     journal = {Elemente der Mathematik},
     pages = {65--65},
     publisher = {mathdoc},
     volume = {17},
     year = {1962},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1962__17_140750/}
}