OHM, Jack; RUSH, David E. Content Modules and Algebras. Mathematica Scandinavica, Berkeley, CA, United States, v. 31, p. 49–68, 1972. DOI: 10.7146/math.scand.a-11411. Disponível em: https://journals.msp.org/mscand/article/view/2234. Acesso em: 25 jul. 2026.