@book{PPN243240503, title = {Gesammelte mathematische Abhandlungen 1}, series = {GDML\_Books}, year = {1921}, language = {ger}, url = {http://dml.mathdoc.fr/item/PPN243240503} }
(éd.). Gesammelte mathematische Abhandlungen 1. GDML_Books (1921), http://gdmltest.u-ga.fr/item/PPN243240503/