BELL, Howard E.; KLEIN, Abraham A. Some noteworthy examples of zero divisors in infinite rings II. Mathematica Scandinavica, Berkeley, CA, United States, v. 83, n. 2, p. 161–168, 1998. DOI: 10.7146/math.scand.a-13847. Disponível em: https://journals.msp.org/mscand/article/view/981. Acesso em: 25 jul. 2026.