@article{GDZPPN002226413, title = {Dupin'sche Hyperfl\"achen in E4.}, journal = {Manuscripta mathematica}, volume = {53}, year = {1985}, pages = {89-120}, zbl = {0572.53028}, url = {http://dml.mathdoc.fr/item/GDZPPN002226413} }
Pinkall, Ulrich. Dupin'sche Hyperflächen in E4.. Manuscripta mathematica, Tome 53 (1985) pp. 89-120. http://gdmltest.u-ga.fr/item/GDZPPN002226413/