@article{MAN_1897__49_157847,
     author = {Paul St\"ackel and Friedrich Engel},
     title = {Gauss, die beiden {Bolyai} und die nichteuklidische {Geometrie} .},
     journal = {Mathematische Annalen},
     pages = {149--206},
     publisher = {mathdoc},
     volume = {49},
     year = {1897},
     zbl = {28.0042.02},
     url = {http://geodesic.mathdoc.fr/item/MAN_1897__49_157847/}
}