@article{MAN_1871__4_156553,
     author = {Klein},
     title = {Ueber die sogenannte {Nicht-Euklidische} {Geometrie}},
     journal = {Mathematische Annalen},
     pages = {573--625},
     year = {1871},
     volume = {4},
     language = {de},
     url = {http://geodesic.mathdoc.fr/item/MAN_1871__4_156553/}
}