Columbia subject headings:
Harvard subject headings:
Electric power--Portugal--History--19th century.
Electric power--Portugal--History--20th century.
Electricity--History
Electrification--Portugal--History--19th century.
Electrification--Portugal--History--20th century.
Princeton subject headings:
Electric power--Portugal--History--19th century.
Electric power--Portugal--History--20th century.
Electricity--History.
Electrification--Portugal--History--19th century.
Electrification--Portugal--History--20th century.