%0 Journal Article %A Leutola, K. %A Nieminen, J. %T Relations, coverings, hypergraphs and matroids %J Czechoslovak Mathematical Journal %D 1983 %P 509-518 %V 33 %N 4 %I mathdoc %U http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1983.101906/ %R 10.21136/CMJ.1983.101906 %G en %F 10_21136_CMJ_1983_101906