@article{MM2_1985__51_155066,
     author = {Ulrich Pinkall},
     title = {Dupin'sche {Hyperfl\"achen} in {E4.}},
     journal = {Manuscripta mathematica},
     pages = {89--120},
     publisher = {mathdoc},
     volume = {51},
     year = {1985},
     zbl = {0572.53028},
     url = {http://geodesic.mathdoc.fr/item/MM2_1985__51_155066/}
}