@article{PPN37649882X+dmdlog70, title = {2. Die Ber\"uhrungstransformationen.}, booktitle = {Geometrie Bd. 2}, series = {GDML\_Books}, year = {1968}, pages = {119}, url = {http://dml.mathdoc.fr/item/PPN37649882X+dmdlog70} }
(éd.). 2. Die Berührungstransformationen., dans Geometrie Bd. 2, GDML_Books, (1968), p. 119. http://gdmltest.u-ga.fr/item/PPN37649882X+dmdlog70/