Columbia subject headings:
P.S.O.E. (Political party)--History.
Socialism--Spain--History.
Harvard subject headings:
P.S.O.E. (Political party)--History.
Socialism--Spain
Socialism--Spain--History
Spain--Politics and government--19th century.
Spain--Politics and government--20th century.
Princeton subject headings:
P.S.O.E. (Political party)--History.
Spain--Politics and government--19th century.
Spain--Politics and government--20th century.