Cita APA (7a ed.)

Duncan, D. (1908). Life and letters of Herbert Spencer. D. Appleton and Company.

Cita Chicago Style (17a ed.)

Duncan, David. Life and Letters of Herbert Spencer. New York: D. Appleton and Company, 1908.

Cita MLA (9a ed.)

Duncan, David. Life and Letters of Herbert Spencer. D. Appleton and Company, 1908.