BELL, Howard E.; KLEIN, Abraham A. Some noteworthy examples of zero divisors in infinite rings II. MATHEMATICA SCANDINAVICA, [S. l.], v. 83, n. 2, p. 161–168, 1998. DOI: 10.7146/math.scand.a-13847. Disponível em: https://www.mscand.dk/article/view/13847. Acesso em: 5 dec. 2025.