Columbia subject headings:
Drug control--England--History--19th century.
Drug control--England--History--20th century.
Opium abuse--England--History--19th century.
Opium abuse--England--History--20th century.
Opium trade--England--History--19th century.
Opium trade--England--History--20th century.
Harvard subject headings:
Drug control--England--History--19th century.
Opium abuse--England--History--19th century.
Opium trade--England--History--19th century.
Princeton subject headings: