@article{ELMA_1987__42_4_141401,
     author = {Helmut Pottmann},
     title = {\"Uber geschlossene sph\"arische {Kurven.}},
     journal = {Elemente der Mathematik},
     pages = {62--68},
     publisher = {mathdoc},
     volume = {42},
     number = {4},
     year = {1987},
     zbl = {0699.53003},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1987__42_4_141401/}
}