Cita APA (7a ed.)

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

Cita Chicago Style (17a ed.)

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

Cita MLA (9a ed.)

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