Columbia subject headings:
Industries--Social aspects--Spain.
Industries--Spain--Statistics.
Work--Spain--History--19th century.
Work--Spain--History--20th century.
Work--Spain--Statistics.
Harvard subject headings:
Labor--Spain--History--19th century.
Labor--Spain--History--20th century.
Labor--Spain--Statistics.
Princeton subject headings:
Industrial statistics--Spain.
Industries--Social aspects--Spain.
Labor--Spain--History--19th century.
Labor--Spain--History--20th century.
Labor--Spain--Statistics.