%0 Journal Article
%A JACOB NIELSEN
%T A basis for subgroups of free groups
%J Mathematica Scandinavica
%D 1955
%P 31-43
%V 3
%I mathdoc
%U http://geodesic.mathdoc.fr/item/MS2_1955__3_165565/
%F MS2_1955__3_165565