Columbia subject headings:
Freight and freightage--Europe--Congresses.
Transportation and state--Europe--Congresses.
Transportation--Europe--Congresses.
Harvard subject headings:
Freight and freightage--Europe--Congresses.
Transportation and state--Europe--Congresses.
Transportation--Europe--Congresses
Princeton subject headings:
Freight and freightage--Europe--Congresses.
Transportation and state--Europe--Congresses.
Transportation--Europe--Congresses.