Lam, Tsit-Yuen (1999). 《Lectures on modules and rings》. Graduate Texts in Mathematics No. 189 (영어). Springer. ISBN978-0-387-98428-5. MR1653294.
Baer, Reinhold (1940). “Abelian groups that are direct summands of every containing abelian group”. 《Bulletin of the American Mathematical Society》 (영어) 46 (10): 800–807. doi:10.1090/S0002-9904-1940-07306-9. MR0002886. Zbl0024.14902.
doi.org
dx.doi.org
Baer, Reinhold (1940). “Abelian groups that are direct summands of every containing abelian group”. 《Bulletin of the American Mathematical Society》 (영어) 46 (10): 800–807. doi:10.1090/S0002-9904-1940-07306-9. MR0002886. Zbl0024.14902.
zbmath.org
Baer, Reinhold (1940). “Abelian groups that are direct summands of every containing abelian group”. 《Bulletin of the American Mathematical Society》 (영어) 46 (10): 800–807. doi:10.1090/S0002-9904-1940-07306-9. MR0002886. Zbl0024.14902.