Columbia subject headings:
Petroleum industry and trade--United States--History--Sources.
Petroleum workers--United States--History--Sources.
Petroleum workers--United States--Interviews.
Harvard subject headings:
Petroleum industry and trade--United States--History--Sources.
Petroleum workers--United States--History--Sources.
Petroleum workers--United States--Interviews.
Princeton subject headings:
Petroleum industry and trade--United States--History--Sources.
Petroleum workers--United States--History--Sources.
Petroleum workers--United States--Interviews.