@book{PPN590099280, title = {F\"ur mittlere Klassen H. 1}, series = {GDML\_Books}, publisher = {Stein}, address = {Potsdam}, year = {1883}, language = {de}, url = {http://dml.mathdoc.fr/item/PPN590099280} }
Schubert, Hermann. Für mittlere Klassen H. 1. GDML_Books (1883), http://gdmltest.u-ga.fr/item/PPN590099280/