Columbia subject headings:
País Vasco (Spain)--History.
País Vasco (Spain)--Politics and government.
Socialism--Spain--País Vasco--History--20th century.
Harvard subject headings:
Socialism--Spain--País Vasco--History.
Socialism--Spain--País Vasco.
Princeton subject headings:
P.S.O.E. (Political party)--History.
País Vasco (Spain)--Politics and government.
Socialism--Spain--History.
Socialism--Spain--País Vasco--History.