@article{MZ_1976__150_172421,
     author = {Oswald Giering and Hubert Frank},
     title = {Verallgemeinerte {Regelfl\"achen.}},
     journal = {Mathematische Zeitschrift},
     pages = {261--272},
     publisher = {mathdoc},
     volume = {150},
     year = {1976},
     zbl = {0331.53011},
     url = {http://geodesic.mathdoc.fr/item/MZ_1976__150_172421/}
}