Columbia subject headings:
Geochemical prospecting.
Natural gas--Geology.
Petroleum--Geology.
Harvard subject headings:
Geochemical prospecting.
Natural gas--Geology
Natural gas--Prospecting
Petroleum--Geology
Petroleum--Prospecting
Princeton subject headings:
Geochemical prospecting.
Natural gas--Geology.
Natural gas--Prospecting.
Petroleum--Geology.
Petroleum--Prospecting.