@article{10_4064_aa_19_3_307_309,
     author = {David Lubell},
     title = {On a density problem of {Erd\"os}},
     journal = {Acta Arithmetica},
     pages = {307--309},
     publisher = {mathdoc},
     volume = {19},
     number = {3},
     year = {1971},
     doi = {10.4064/aa-19-3-307-309},
     language = {de},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/aa-19-3-307-309/}
}