%0 Journal Article %A Pondělíček, Bedřich %T A Relation for Closure Operations on a Semigroup %J Mathematica slovaca %D 1973 %P 249-256 %V 23 %N 3 %I mathdoc %U http://geodesic.mathdoc.fr/item/MASLO_1973__23_3_a7/ %G en %F MASLO_1973__23_3_a7