%0 Journal Article %A Ježek, Jaroslav %T The existence of upper semicomplements in lattices of primitive classes %J Commentationes Mathematicae Universitatis Carolinae %D 1971 %P 519-532 %V 12 %N 3 %I mathdoc %U http://geodesic.mathdoc.fr/item/CMUC_1971__12_3_a4/ %G en %F CMUC_1971__12_3_a4