@book{PPN622650963, title = {Kongruenz Heft 1}, series = {GDML\_Books}, publisher = {Nebert}, address = {Halle}, year = {1889}, language = {de}, url = {http://dml.mathdoc.fr/item/PPN622650963} }
Köstler, Hermann J. Kongruenz Heft 1. GDML_Books (1889), http://gdmltest.u-ga.fr/item/PPN622650963/