@article{IM_1987__90_143524,
     author = {D.W. Lewis},
     title = {Witt rings as integral rings.},
     journal = {Inventiones mathematicae},
     pages = {631--634},
     publisher = {mathdoc},
     volume = {90},
     year = {1987},
     zbl = {0629.10017},
     url = {http://geodesic.mathdoc.fr/item/IM_1987__90_143524/}
}