@article{10_4153_CJM_1990_047_5,
     author = {Just, Winfried},
     title = {Repercussions of a {Problem} of {Erd\H{o}s} and {Ulam} on {Density} {Ideals}},
     journal = {Canadian journal of mathematics},
     pages = {902--914},
     year = {1990},
     volume = {42},
     number = {5},
     doi = {10.4153/CJM-1990-047-5},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1990-047-5/}
}