%0 Journal Article
%A Gruska, Jozef
%T Grammatical levels and subgrammars of context-free grammars
%J Archivum mathematicum
%D 1973
%P 19-21
%V 9
%N 1
%U http://geodesic.mathdoc.fr/item/ARM_1973_9_1_a2/
%G en
%F ARM_1973_9_1_a2