Voir la notice de l'article provenant de la source European Digital Mathematics Library
@article{CMH_1934__6_138608, author = {L. Locher}, title = {Die {Untergruppen} der freien {Gruppen.}}, journal = {Commentarii mathematici Helvetici}, pages = {76--82}, publisher = {mathdoc}, volume = {6}, year = {1934}, zbl = {0007.10203}, url = {http://geodesic.mathdoc.fr/item/CMH_1934__6_138608/} }
L. Locher. Die Untergruppen der freien Gruppen.. Commentarii mathematici Helvetici, Tome 6 (1934), pp. 76-82. http://geodesic.mathdoc.fr/item/CMH_1934__6_138608/