Columbia subject headings:
Foreign trade regulation--Handbooks, manuals, etc.
Free ports and zones--United States--Handbooks, manuals, etc.
U.S. Customs Service--Handbooks, manuals, etc.
Harvard subject headings:
Foreign trade regulation--United States--Handbooks, manuals, etc.
Free ports and zones--United States--Handbooks, manuals, etc.
U.S. Customs Service--Handbooks, manuals, etc.
Princeton subject headings: