@article{GDZPPN00248448X, title = {Covering Sets by Subsets.}, journal = {Monatshefte f\"ur Mathematik}, volume = {98}, year = {1984}, pages = {323-330}, zbl = {0545.05006}, url = {http://dml.mathdoc.fr/item/GDZPPN00248448X} }
Warlimont, Richard. Covering Sets by Subsets.. Monatshefte für Mathematik, Tome 98 (1984) pp. 323-330. http://gdmltest.u-ga.fr/item/GDZPPN00248448X/