APA (7th ed.) Citation

Spencer, H. (1910). The principles of psychology (3d ed.). D. Appleton.

Chicago Style (17th ed.) Citation

Spencer, Herbert. The Principles of Psychology. 3d ed. New York: D. Appleton, 1910.

MLA (9th ed.) Citation

Spencer, Herbert. The Principles of Psychology. 3d ed. D. Appleton, 1910.