Columbia subject headings:
Gas industry--Statistics--Periodicals.
Petroleum industry and trade--Statistics--Periodicals.
Power resources--Statistics--Periodicals.
Harvard subject headings:
Gas industry--Statistics--Periodicals.
Petroleum industry and trade--Statistics--Periodicals.
Power resources--Statistics--Periodicals.
Princeton subject headings:
Gas industry--Statistics--Periodicals.
Periodicals.
Petroleum industry and trade--Statistics--Periodicals.
Power resources--Statistics--Periodicals.
Statistics.