%0 Journal Article
%A Ježek, Jaroslav
%T Upper semicomplements and a definable element in the lattice of groupoid varieties
%J Commentationes Mathematicae Universitatis Carolinae
%D 1971
%P 565-586
%V 12
%N 3
%I mathdoc
%U http://geodesic.mathdoc.fr/item/CMUC_1971__12_3_a8/
%G en
%F CMUC_1971__12_3_a8