%0 Journal Article
%T [unknown]
%J Acta mathematica Universitatis Comenianae
%D 1989
%P 285-289
%V 54-55
%I mathdoc
%U http://geodesic.mathdoc.fr/item/AMUC_1989__54-55_186042/
%F AMUC_1989__54-55_186042