GRANIRER, E.; RAJAGOPALAN, M. A Note on the Radical of the Second Conjugate Algebra of a Semigroup Algebra. MATHEMATICA SCANDINAVICA, [S. l.], v. 15, p. 163–166, 1964. DOI: 10.7146/math.scand.a-10740. Disponível em: https://www.mscand.dk/article/view/10740. Acesso em: 6 may. 2024.