@article{GDZPPN002055783,
title = {A Theorem on Orientable Surfaces in Four-Dimensional Space.},
journal = {Commentarii mathematici Helvetici},
volume = {25},
year = {1951},
pages = {205-209},
zbl = {0043.38403},
url = {http://dml.mathdoc.fr/item/GDZPPN002055783}
}
Chern, Shiing-Shen; Spanier, E. A Theorem on Orientable Surfaces in Four-Dimensional Space.. Commentarii mathematici Helvetici, Tome 25 (1951) pp. 205-209. http://gdmltest.u-ga.fr/item/GDZPPN002055783/