APA (7th ed.) Citation

Willoughby, W. W. (1925). Opium as an international problem: The Geneva conferences. Johns Hopkins Press.

Chicago Style (17th ed.) Citation

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

MLA (9th ed.) Citation

Willoughby, Westel Woodbury. Opium as an International Problem: The Geneva Conferences. Johns Hopkins Press, 1925.