@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/