@article{GDZPPN002259516, title = {A fundamental theorem in the theory of ruled surfaces}, journal = {Mathematische Annalen}, volume = {58}, year = {1904}, pages = {249-256}, url = {http://dml.mathdoc.fr/item/GDZPPN002259516} }
Wilczynski, E.J. A fundamental theorem in the theory of ruled surfaces. Mathematische Annalen, Tome 58 (1904) pp. 249-256. http://gdmltest.u-ga.fr/item/GDZPPN002259516/