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