@article{GDZPPN002051656, title = {Zur Theorie der Bewegungsgruppen.}, journal = {Commentarii mathematici Helvetici}, volume = {7}, year = {1934}, pages = {159-184}, language = {de}, url = {http://dml.mathdoc.fr/item/GDZPPN002051656} }
Burckhardt, J.J. Zur Theorie der Bewegungsgruppen.. Commentarii mathematici Helvetici, Tome 7 (1934) pp. 159-184. http://gdmltest.u-ga.fr/item/GDZPPN002051656/