%0 Journal Article
%A Eric Mendelsohn
%T An Elementary Characterization of the Category of (Free) Relational Systems.
%J Mathematische Zeitschrift
%D 1970
%P 224-232
%V 113
%I mathdoc
%U http://geodesic.mathdoc.fr/item/MZ_1970__113_171271/
%F MZ_1970__113_171271