Columbia subject headings:
Metallurgy--Congresses.
Mineralogy, Determinative--Congresses.
Power resources--Congresses.
Prospecting--Congresses.
Harvard subject headings:
Metallurgy--Congresses.
Mineralogy, Determinative--Congresses
Power resources--Congresses
Prospecting--Congresses
Princeton subject headings:
Mineral industries--Congresses.
Mines and mineral resources--Congresses.
Power resources--Congresses.