@article{10_4153_CMB_1972_005_4,
     author = {Erd\"os, P.},
     title = {On a {Problem} of {Gro\"ubaum}},
     journal = {Canadian mathematical bulletin},
     pages = {23--25},
     year = {1972},
     volume = {15},
     number = {1},
     doi = {10.4153/CMB-1972-005-4},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1972-005-4/}
}