singer, p. (1993). Practical Ethics (2nd.). cambridge University Press.
Cita Chicago (17th ed.)singer, peter. Practical Ethics. 2nd. Cambridge: cambridge University Press, 1993.
Cita MLA (9th ed.)singer, peter. Practical Ethics. 2nd. cambridge University Press, 1993.
Atenció: Aquestes cites poden no estar 100% correctes.