@book{PPN584694482, title = {Trigonometrie Th. 3}, series = {GDML\_Books}, publisher = {Zwissler}, address = {Wolfenb\"uttel}, year = {1880}, language = {de}, url = {http://dml.mathdoc.fr/item/PPN584694482} }
Schlegel, Victor. Trigonometrie Th. 3. GDML_Books (1880), http://gdmltest.u-ga.fr/item/PPN584694482/