%0 Journal Article
%A Karrass, A.
%A Pietrowski, A.
%A Solitar, D.
%T An Improved Subgroup Theorem for HNN Groups with Some Applications
%J Canadian journal of mathematics
%D 1974
%P 214-224
%V 26
%N 1
%U http://geodesic.mathdoc.fr/articles/10.4153/CJM-1974-021-1/
%R 10.4153/CJM-1974-021-1
%F 10_4153_CJM_1974_021_1