%0 Journal Article
%A J. Wallbaum
%T A~$\Delta^0_2$-poset with no positive presentation
%J Algebra i logika
%D 2012
%P 423-428
%V 51
%N 4
%I mathdoc
%U http://geodesic.mathdoc.fr/item/AL_2012_51_4_a0/
%G ru
%F AL_2012_51_4_a0