Cita APA (7a ed.)

Spencer, H. (1900). The principles of ethics. Williams & Norgate.

Cita Chicago Style (17a ed.)

Spencer, Herbert. The Principles of Ethics. London [etc.]: Williams & Norgate, 1900.

Cita MLA (9a ed.)

Spencer, Herbert. The Principles of Ethics. Williams & Norgate, 1900.