PLONKA, Ernest. On a Non-Abelian Variety of Groups which are Symmetric Algebras. Mathematica Scandinavica, Berkeley, CA, United States, v. 74, p. 184–190, 1994. DOI: 10.7146/math.scand.a-12488. Disponível em: https://journals.msp.org/mscand/article/view/1135. Acesso em: 24 jul. 2026.