Columbia subject headings:
Harvard subject headings:
Caspian Sea Region--Politics and government--20th century.
Caspian Sea Region--Strategic aspects.
Gas industry--Caspian Sea Region.
Geopolitics--Caspian Sea Region.
Petroleum industry and trade--Political aspects--Caspian Sea Region.
Princeton subject headings:
Caspian Sea Region--Politics and government--20th century.
Caspian Sea Region--Strategic aspects.
Gas industry--Caspian Sea Region.
Geopolitics--Caspian Sea Region.
Petroleum industry and trade--Political aspects--Caspian Sea Region.