@article{ELMA_1981__36_141268,
     author = {O. Bottema and J.T. Groenman},
     title = {On the upward motion of a double cone on an inclined plane.},
     journal = {Elemente der Mathematik},
     pages = {121--126},
     publisher = {mathdoc},
     volume = {36},
     year = {1981},
     zbl = {0467.53005},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1981__36_141268/}
}