@book{PPN589772813, title = {Die Planimetrie Band 2, Theil 2}, series = {GDML\_Books}, publisher = {Hahn}, year = {1862}, language = {de}, url = {http://dml.mathdoc.fr/item/PPN589772813} }
Helmes, Joseph. Die Planimetrie Band 2, Theil 2. GDML_Books (1862), http://gdmltest.u-ga.fr/item/PPN589772813/