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@article{CMH_1942__15_138799, author = {Heinz Hopf}, title = {Maximale {Toroide} und singul\"are {Elemente} in geschlossenen {Lieschen} {Gruppen.}}, journal = {Commentarii mathematici Helvetici}, pages = {59--70}, publisher = {mathdoc}, volume = {15}, year = {1942}, zbl = {0027.09601}, url = {http://geodesic.mathdoc.fr/item/CMH_1942__15_138799/} }
Heinz Hopf. Maximale Toroide und singuläre Elemente in geschlossenen Lieschen Gruppen.. Commentarii mathematici Helvetici, Tome 15 (1942), pp. 59-70. http://geodesic.mathdoc.fr/item/CMH_1942__15_138799/