@book{PPN589855646, title = {Astronomische und optische Abhandlungen Bd. 3}, series = {GDML\_Books}, publisher = {D\"ummler}, address = {Berlin}, year = {1889}, language = {de}, url = {http://dml.mathdoc.fr/item/PPN589855646} }
Encke, Johann Franz. Astronomische und optische Abhandlungen Bd. 3. GDML_Books (1889), http://gdmltest.u-ga.fr/item/PPN589855646/