@article{GDZPPN002074753,
title = {Ungel\"oste Probleme.},
journal = {Elemente der Mathematik},
volume = {16},
year = {1961},
pages = {30-31},
url = {http://dml.mathdoc.fr/item/GDZPPN002074753}
}
Hadwiger, H. Ungelöste Probleme.. Elemente der Mathematik, Tome 16 (1961) pp. 30-31. http://gdmltest.u-ga.fr/item/GDZPPN002074753/