如题，摘要如下。整个课程涵盖了近期国际贸易最前沿的研究，大多数讲义中讨论的文章，在2013年时候为顶级杂志forthcoming状态，如今2015年，也并未淘汰。讲义中，更为系统化的是，Melitz 自己给出了完整的一套做企业异质性所必须的数学知识，使得对异质性了解不深的同学，仍能从基础学起，很快读懂国际贸易最热门问题中的理论推导。
Recent empirical evidence has shown that firms/plants producing similar goods react very differently to international forces.  Some firms export, while others only serve their domestic market.  Among the former, a small subset export to a large number of international markets while a substantial proportion of exporters only serve a single foreign market.  Other firms (multinationals) choose to serve customers in foreign markets via local subsidiaries.  Trade, and international forces more generally, thus induce important composition changes within industries, leading to substantial measured changes in economic performance.  The lectures will survey the newer empirical literature based on firm-level studies of trade, and develop the analytical framework for general equilibrium models of trade with heterogeneous producers.  The lectures will then cover applications (both theoretical and empirical) of these models to different subfields of international economics.