@article{ELMA_1994__49_1_141566,
     author = {Beno Eckmann},
     title = {Zum 100. {Geburtstag} von {Heinz} {Hopf.}},
     journal = {Elemente der Mathematik},
     pages = {133--136},
     year = {1994},
     volume = {49},
     number = {1},
     zbl = {0826.01016},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1994__49_1_141566/}
}