%0 Journal Article
%A G. P. Gavrilov
%T On the cardinality of sets of closed classes of finite height in $P_{\aleph_0}$
%J Doklady Akademii Nauk
%D 1964
%P 503-506
%V 158
%N 3
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DAN_1964_158_3_a0/
%G ru
%F DAN_1964_158_3_a0