OHM, Jack; RUSH, David E. Content Modules and Algebras. MATHEMATICA SCANDINAVICA, [S. l.], v. 31, p. 49–68, 1972. DOI: 10.7146/math.scand.a-11411. Disponível em: https://www.mscand.dk/article/view/11411. Acesso em: 5 dec. 2025.