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