MAGARIAN, E. A. Direct Limits of Power Series Rings. MATHEMATICA SCANDINAVICA, [S. l.], v. 31, p. 103–110, 1972. DOI: 10.7146/math.scand.a-11416. Disponível em: https://www.mscand.dk/article/view/11416. Acesso em: 8 may. 2024.