Willoughby, W. W. (1925). Opium as an international problem, the Geneva conferences. John Hopkins Press.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रWilloughby, Westel Woodbury. Opium as an International Problem, the Geneva Conferences. Baltimore: John Hopkins Press, 1925.
एमएलए (9वां संस्करण) प्रशस्ति पत्रWilloughby, Westel Woodbury. Opium as an International Problem, the Geneva Conferences. John Hopkins Press, 1925.
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