@article{ELMA_1963__18_140781,
     author = {H. Lenz},
     title = {Ungel\"oste {Probleme.}},
     journal = {Elemente der Mathematik},
     pages = {134--134},
     publisher = {mathdoc},
     volume = {18},
     year = {1963},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1963__18_140781/}
}