Columbia subject headings:
Labor policy--Spain--History--Sources.
Labor unions--Spain--History--Sources.
Syndicalism--Spain--History--Sources.
Harvard subject headings:
Labor policy--Spain--History--Sources.
Labor unions--Spain--History--Sources.
Syndicalism--Spain--History--Sources.
Princeton subject headings:
Labor policy--Spain--History--Sources.
Labor unions--Spain--History--Sources.
Syndicalism--Spain--History--Sources.