Columbia subject headings:
P.S.O.E. (Political party)--History--21st century.
Political parties--Spain--History--21st century.
Socialism--Spain--History--21st century.
Harvard subject headings:
P.S.O.E. (Political party)--History--21st century.
Political parties--Spain--History--21st century.
Socialism--Spain--History--21st century.
Princeton subject headings:
P.S.O.E. (Political party)--History--21st century.
Political parties--Spain--History--21st century.
Socialism--Spain--History--21st century.