TON, Dao-rong; HE, Kai-yao. Free Archimedean $l$-Groups. Mathematica Scandinavica, Berkeley, CA, United States, v. 74, p. 34–48, 1994. DOI: 10.7146/math.scand.a-12478. Disponível em: https://journals.msp.org/mscand/article/view/1145. Acesso em: 25 jul. 2026.