公共承运人

受款人

股东

成本经济

差别待遇

循环信用证

管理合同

证券交易所

发票

Tariff barriers are the most common form of trade restriction.A tariff is a tax levied on a commodity when it crosses the boundary of a customs area which usually coincides with the area of a country.A customs area extending beyond national boundaries to include two or more independent nations is called a customs union.