@article{MAN_1875__9_156700,
     author = {B\"acklund},
     title = {Ueber {Fl\"achentransformationen}},
     journal = {Mathematische Annalen},
     pages = {297--320},
     publisher = {mathdoc},
     volume = {9},
     year = {1875},
     url = {http://geodesic.mathdoc.fr/item/MAN_1875__9_156700/}
}