@article{MAN_1904__58_158123,
     author = {E.J. Wilczynski},
     title = {A fundamental theorem in the theory of ruled surfaces},
     journal = {Mathematische Annalen},
     pages = {249--256},
     publisher = {mathdoc},
     volume = {58},
     year = {1904},
     url = {http://geodesic.mathdoc.fr/item/MAN_1904__58_158123/}
}