@article{GDZPPN002074222, title = {Ungel\"oste Probleme.}, journal = {Elemente der Mathematik}, volume = {13}, year = {1958}, pages = {13-14}, url = {http://dml.mathdoc.fr/item/GDZPPN002074222} }
Hadwiger, H. Ungelöste Probleme.. Elemente der Mathematik, Tome 13 (1958) pp. 13-14. http://gdmltest.u-ga.fr/item/GDZPPN002074222/