@book{PPN590873717, title = {Das graphische Rechnen Theil 1}, series = {GDML\_Books}, publisher = {Calve}, address = {Prag}, year = {1879}, language = {de}, url = {http://dml.mathdoc.fr/item/PPN590873717} }
Ott, Karl. Das graphische Rechnen Theil 1. GDML_Books (1879), http://gdmltest.u-ga.fr/item/PPN590873717/