Columbia subject headings:
Gas industry--Canada--Periodicals.
Natural gas--Canada.
Petroleum industry and trade--Canada--Periodicals.
Harvard subject headings:
Gas industry--Canada--Periodicals.
Natural gas--Canada
Petroleum industry and trade--Canada--Periodicals.
Princeton subject headings:
Gas industry--Canada--Periodicals.
Natural gas--Canada--Periodicals.
Petroleum industry and trade--Canada--Periodicals.