Cita APA (7a ed.)

Singer, P. (2011). The Expanding circle: Ethics, evolution, and moral progress. Princeton University Press.

Cita Chicago Style (17a ed.)

Singer, Peter. The Expanding Circle: Ethics, Evolution, and Moral Progress. Princeton ; Oxford: Princeton University Press, 2011.

Cita MLA (9a ed.)

Singer, Peter. The Expanding Circle: Ethics, Evolution, and Moral Progress. Princeton University Press, 2011.