@article{MAN_1904__58_158141,
     author = {Siegfried Heller},
     title = {Untersuchungen \"uber die nat\"urlichen {Gleichungen} krummer {Fl\"achen.}},
     journal = {Mathematische Annalen},
     pages = {565--577},
     publisher = {mathdoc},
     volume = {58},
     year = {1904},
     zbl = {35.0616.02},
     url = {http://geodesic.mathdoc.fr/item/MAN_1904__58_158141/}
}