%0 Journal Article
%A Shiing-Shen Chern
%A E. Spanier
%T A Theorem on Orientable Surfaces in Four-Dimensional Space.
%J Commentarii mathematici Helvetici
%D 1951
%P 205-209
%V 25
%I mathdoc
%U http://geodesic.mathdoc.fr/item/CMH_1951__25_139026/
%F CMH_1951__25_139026