Columbia subject headings:
Petroleum industry and trade--History--19th century.
Petroleum industry and trade--History--20th century.
Shell Transport and Trading Company.
Harvard subject headings:
Petroleum industry and trade--History--19th century.
Petroleum industry and trade--History--20th century.
Shell Transport and Trading Company
Princeton subject headings:
Koninklijke Nederlandsche Petroleum Maatschappij--History.
Petroleum industry and trade--History.
Shell Transport and Trading Company--History.