%0 Journal Article %A Porubský, Štefan %T Identities involving covering systems. I. %J Mathematica slovaca %D 1994 %P 153-162 %V 44 %N 2 %I mathdoc %U http://geodesic.mathdoc.fr/item/MASLO_1994__44_2_a5/ %G en %F MASLO_1994__44_2_a5