@article{IM_1988__91_3_143553,
     author = {B.A. Magurn and W. Van der Kallen},
     title = {Absolute stable rank and {Witt} cancellation for noncommutative rings.},
     journal = {Inventiones mathematicae},
     pages = {525--542},
     publisher = {mathdoc},
     volume = {91},
     number = {3},
     year = {1988},
     zbl = {0639.16015},
     url = {http://geodesic.mathdoc.fr/item/IM_1988__91_3_143553/}
}