@article{GDZPPN002073935, title = {Ungel\"oste Probleme.}, journal = {Elemente der Mathematik}, volume = {11}, year = {1956}, pages = {60-61}, url = {http://dml.mathdoc.fr/item/GDZPPN002073935} }
Hadwiger, H. Ungelöste Probleme.. Elemente der Mathematik, Tome 11 (1956) pp. 60-61. http://gdmltest.u-ga.fr/item/GDZPPN002073935/