9Claus Steinle, Holger Schiele, "When do indus- tries cluster? A proposal on how to assess an industry's propensity to concentrate at a single region", Research Policy,2002, 31(6) , 849--858.
10J. Myles Shaver, Fredrick Flyer, "Agglomeration economies, firm heterogeneity, and foreign direct invest- ment in the United States", Strategic Management Jour- nal, 2000,21(1) , 1175--1193.