Columbia subject headings:
Deltas--Soviet Union.
Deltas.
Natural gas--Geology--Soviet Union.
Natural gas--Geology.
Petroleum--Geology--Soviet Union.
Petroleum--Geology.
Harvard subject headings:
Natural gas--Geology
Petroleum--Geology
Sedimentation and deposition.
Sediments (Geology)
Princeton subject headings:
Deltas--Soviet Union.
Deltas.
Natural gas--Geology--Soviet Union.
Natural gas--Geology.
Petroleum--Geology--Soviet Union.
Petroleum--Geology.