@article{GDZPPN002076292, title = {Ungel\"oste Probleme.}, journal = {Elemente der Mathematik}, volume = {23}, year = {1968}, pages = {14-15}, url = {http://dml.mathdoc.fr/item/GDZPPN002076292} }
Hadwiger, H. Ungelöste Probleme.. Elemente der Mathematik, Tome 23 (1968) pp. 14-15. http://gdmltest.u-ga.fr/item/GDZPPN002076292/