@article{MAN_1880__17_156934,
     author = {in Petersburg. Markoff},
     title = {Sur les formes quadratiques binaires indefinies. {(Second} m\'emoire)},
     journal = {Mathematische Annalen},
     pages = {379--399},
     year = {1880},
     volume = {17},
     url = {http://geodesic.mathdoc.fr/item/MAN_1880__17_156934/}
}