@article{GDZPPN002073870,
title = {Ungel\"oste Probleme.},
journal = {Elemente der Mathematik},
volume = {11},
year = {1956},
pages = {15-17},
url = {http://dml.mathdoc.fr/item/GDZPPN002073870}
}
Hadwiger, H. Ungelöste Probleme.. Elemente der Mathematik, Tome 11 (1956) pp. 15-17. http://gdmltest.u-ga.fr/item/GDZPPN002073870/