Voir la notice de l'article provenant de la source European Digital Mathematics Library
@article{CMH_1940__13_138770, author = {Heinz Hopf}, title = {Ein topologischer {Beitrag} zur reellen {Algebra.}}, journal = {Commentarii mathematici Helvetici}, pages = {219--239}, publisher = {mathdoc}, volume = {13}, year = {1940}, zbl = {0024.36002}, url = {http://geodesic.mathdoc.fr/item/CMH_1940__13_138770/} }
Heinz Hopf. Ein topologischer Beitrag zur reellen Algebra.. Commentarii mathematici Helvetici, Tome 13 (1940), pp. 219-239. http://geodesic.mathdoc.fr/item/CMH_1940__13_138770/