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