APA (7th ed.) Citation

Darwin, L. (1921). Organic evolution: Outstanding difficulties and possible explanations. The University Press.

Chicago Style (17th ed.) Citation

Darwin, Leonard. Organic Evolution: Outstanding Difficulties and Possible Explanations. Cambridge [England]: The University Press, 1921.

MLA (9th ed.) Citation

Darwin, Leonard. Organic Evolution: Outstanding Difficulties and Possible Explanations. The University Press, 1921.