Columbia subject headings:
Balance of payments--United States.
Balance of trade--United States.
International economic relations.
Service industries--United States--Statistics.
Service industries--United States.
United States--Commerce.
Harvard subject headings:
Balance of payments--United States
Balance of trade--United States
Invisible items of trade--United States.
Service industries--United States
United States--Commerce.
Princeton subject headings:
Balance of trade--United States.
Service industries--United States.
United States--Commerce.