APA (7th ed.) Citation

Spencer, H. (1899). The principles of psychology / by Herbert Spencer (4th ed.). Williams & Norgate.

Chicago Style (17th ed.) Citation

Spencer, Herbert. The Principles of Psychology / by Herbert Spencer. 4th ed. London: Williams & Norgate, 1899.

MLA (9th ed.) Citation

Spencer, Herbert. The Principles of Psychology / by Herbert Spencer. 4th ed. Williams & Norgate, 1899.

Warning: These citations may not always be 100% accurate.