@article{CMH_1940__13_138769,
     author = {Eduard Stiefel},
     title = {\"Uber {Richtungsfelder} in den projektiven {R\"aumen} und einen {Satz} aus der reellen {Algebra.}},
     journal = {Commentarii mathematici Helvetici},
     pages = {201--218},
     publisher = {mathdoc},
     volume = {13},
     year = {1940},
     zbl = {0024.36001},
     url = {http://geodesic.mathdoc.fr/item/CMH_1940__13_138769/}
}