APA (7th ed.) Citation

Willoughby, W. W. (1925). Opium as an international problem, the Geneva conferences. John Hopkins Press.

Chicago Style (17th ed.) Citation

Willoughby, Westel Woodbury. Opium as an International Problem, the Geneva Conferences. Baltimore: John Hopkins Press, 1925.

MLA (9th ed.) Citation

Willoughby, Westel Woodbury. Opium as an International Problem, the Geneva Conferences. John Hopkins Press, 1925.