(Lam 1999, p. 3) Lam, Tsit Yuen (1999), Lectures on modules and rings, Graduate Texts in Mathematics, vol. 189, New York: Springer-Verlag, pp. xxiv+557, ISBN0-387-98428-3, MR1653294
(Hungerford 1980, p. 190) Hungerford, Thomas W. (1980) [1974], Algebra, Graduate Texts in Mathematics, vol. 73, New York: Springer-Verlag, pp. xxiii+502, ISBN0-387-90518-9, MR0600654 Reprint of the 1974 original