Columbia subject headings:
Oil industries--Europe--History.
Olive oil industry--Europe--History.
Olive oil industry--Spain--History.
Harvard subject headings:
Oil industries--Rome--History--Congresses.
Olive oil industry--Rome--History--Congresses.
Olive oil industry--Spain--History--To 711--Congresses.
Princeton subject headings:
Oil industries--Europe--History.
Olive oil industry--Europe--History.
Olive oil industry--Spain--History.