@article{10_4064_aa107_2_6,
     author = {J\"orn Steuding},
     title = {Upper bounds for the density of universality},
     journal = {Acta Arithmetica},
     pages = {195--202},
     publisher = {mathdoc},
     volume = {107},
     number = {2},
     year = {2003},
     doi = {10.4064/aa107-2-6},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/aa107-2-6/}
}