@book{PPN592286312, title = {Ebene Geometrie und Trigonometrie Abth. 2}, series = {GDML\_Books}, publisher = {Hahn}, year = {1847}, language = {de}, url = {http://dml.mathdoc.fr/item/PPN592286312} }
Ludowieg, Johann Carl Hermann. Ebene Geometrie und Trigonometrie Abth. 2. GDML_Books (1847), http://gdmltest.u-ga.fr/item/PPN592286312/