@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/