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