@article{GDZPPN002073528, title = {\"Uber die nat\"urliche Gleichung R(s) = ...a (... + cos...).}, journal = {Elemente der Mathematik}, volume = {9}, year = {1954}, pages = {56-63}, zbl = {0056.14901}, url = {http://dml.mathdoc.fr/item/GDZPPN002073528} }
Klepper, W. Über die natürliche Gleichung R(s) = ...a (... + cos...).. Elemente der Mathematik, Tome 9 (1954) pp. 56-63. http://gdmltest.u-ga.fr/item/GDZPPN002073528/