SATYANARAYANA, M. A Note on P.P. Rings. Mathematica Scandinavica, Berkeley, CA, United States, v. 25, p. 105–108, 1969. DOI: 10.7146/math.scand.a-10945. Disponível em: https://journals.msp.org/mscand/article/view/2399. Acesso em: 25 jul. 2026.