%0 Journal Article
%T [unknown]
%J Acta mathematica Universitatis Comenianae
%D 1990
%P 159-166
%V 56-57
%I mathdoc
%U http://geodesic.mathdoc.fr/item/AMUC_1990__56-57_186055/
%F AMUC_1990__56-57_186055