%0 Journal Article
%A Jiri Adamek
%A Vera Trnkova
%T Birkhoff's variety theorem with and without free algebras
%J Theory and applications of categories
%D 2005
%P 424-450
%V 14
%I mathdoc
%U http://geodesic.mathdoc.fr/item/TAC_2005_14_a17/
%G en
%F TAC_2005_14_a17