Columbia subject headings:
Drug control--Periodicals.
Drug control.
Narcotics--Statistics--Periodicals.
Narcotics--Statistics.
Opium trade--Law and legislation.
Opium trade--Periodicals.
Opium--Statistics--Periodicals.
Opium--Statistics.
Harvard subject headings:
Drug control--Periodicals.
Drug control.
Narcotics--Statistics--Periodicals.
Narcotics--Statistics.
Opium trade--Law and legislation
Opium trade--Periodicals.
Opium--Statistics--Periodicals.
Opium--Statistics.
Princeton subject headings: