@article{PPN234735015+dmdlog239, title = {\S . 203. Abz\"ahlbare Mengen}, booktitle = {Lehrbuch der Algebra Bd. 2}, series = {GDML\_Books}, year = {1896}, pages = {745}, url = {http://dml.mathdoc.fr/item/PPN234735015+dmdlog239} }
(éd.). §. 203. Abzählbare Mengen, dans Lehrbuch der Algebra Bd. 2, GDML_Books, (1896), p. 745. http://gdmltest.u-ga.fr/item/PPN234735015+dmdlog239/