@article{ELMA_1954__9_140606,
     author = {W. Klepper},
     title = {\"Uber die nat\"urliche {Gleichung} {R(s)} = ...a (... + cos...).},
     journal = {Elemente der Mathematik},
     pages = {56--63},
     publisher = {mathdoc},
     volume = {9},
     year = {1954},
     zbl = {0056.14901},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1954__9_140606/}
}