@article{AM2_1983__26_136986,
     author = {Howard E. Bell},
     title = {On commutativity of {P.I.} rings.},
     journal = {Aequationes mathematicae},
     pages = {83--88},
     publisher = {mathdoc},
     volume = {26},
     year = {1983},
     zbl = {0537.16028},
     url = {http://geodesic.mathdoc.fr/item/AM2_1983__26_136986/}
}