Columbia subject headings:
Petroleum industry and trade--United States--Directories.
Petroleum industry and trade--United States--Statistics--Periodicals.
Harvard subject headings:
Princeton subject headings:
Directories.
Periodicals.
Petroleum industry and trade--United States--Directories.
Petroleum industry and trade--United States--Periodicals.
Petroleum industry and trade--United States--Statistics.
Petroleum--Periodicals.
Statistics.