@article{MAN_1926__95_159134,
     author = {H. Hopf},
     title = {\"Uber die {Curvatura} integra geschlossener {Hyperfl\"achen}},
     journal = {Mathematische Annalen},
     pages = {340--367},
     publisher = {mathdoc},
     volume = {95},
     year = {1926},
     zbl = {51.0566.02},
     url = {http://geodesic.mathdoc.fr/item/MAN_1926__95_159134/}
}