Columbia subject headings:
Salt industry and trade--History--Congresses.
Salt mines and mining--History--Congresses.
Salt--History--Congresses.
Salt--Social aspects--Congresses.
Harvard subject headings:
Salt industry and trade--History--Congresses.
Salt mines and mining--History--Congresses.
Salt mines and mining--History.
Salt--History--Congresses.
Salt--History.
Salt--Social aspects--Congresses.
Salt--Social aspects--History.
Princeton subject headings: