Columbia subject headings:
Labor unions--Law and legislation--Italy--Florence--History.
Labor unions--Law and legislation--Spain--Castile--History.
Labor unions--Law and legislation--Spain--Valencia--History.
Harvard subject headings:
Labor unions--Law and legislation--Italy--Florence--History.
Labor unions--Law and legislation--Spain--Castile--History.
Labor unions--Law and legislation--Spain--Valencia--History.
Princeton subject headings:
Labor laws and legislation--Italy--History.
Labor laws and legislation--Spain--History.