Columbia subject headings:
Mines and mineral resources--Turkey--Zonguldak.
Zonguldak (Turkey)--Economic conditions.
Harvard subject headings:
Mines and mineral resources--Turkey--Zonguldak.
Zonguldak (Turkey)--Economic conditions.
Princeton subject headings:
Mines and mineral resources--Turkey--Zonguldak.
Zonguldak (Turkey)--Economic conditions.