@article{SLC_1990_25_a9,
     author = {Udo Hebisch und Wilfried Lex},
     title = {Ordnungen nichtkommutativer {Ringe}},
     journal = {S\'eminaire lotharingien de combinatoire},
     publisher = {mathdoc},
     volume = {25},
     year = {1990},
     url = {http://geodesic.mathdoc.fr/item/SLC_1990_25_a9/}
}