@article{MM2_1995__88_1_156128,
     author = {M. Magid and C. Scharlach and L. Vrancken},
     title = {Affine umbilical surfaces in {R4.}},
     journal = {Manuscripta mathematica},
     pages = {275--290},
     publisher = {mathdoc},
     volume = {88},
     number = {1},
     year = {1995},
     zbl = {0852.53014},
     url = {http://geodesic.mathdoc.fr/item/MM2_1995__88_1_156128/}
}