1·There is obvious difference in licence management and tariff tax rate between compound rubber and natural rubber, it brings a certainty difficulty to the custom.
天然橡胶和复合橡胶在许可证管理和关税税率方面存在较大的差异，使海关对复合橡胶的进口监管面临着较大风险。
2·Multilateral Tariff Negotiation and Multilateral Tariff Concession -are the forming of custom unions always increases members' welfare?
多边关税谈判与关税减让——关税同盟的缔结一定会提高成员国的谈判地位吗？