@article{GDZPPN002052695, title = {\"Uber Freisysteme (lineare Freigebilde).}, journal = {Commentarii mathematici Helvetici}, volume = {11}, year = {1938}, pages = {62-76}, zbl = {0019.32503}, url = {http://dml.mathdoc.fr/item/GDZPPN002052695} }
Finsler, Paul. Über Freisysteme (lineare Freigebilde).. Commentarii mathematici Helvetici, Tome 11 (1938) pp. 62-76. http://gdmltest.u-ga.fr/item/GDZPPN002052695/