6HOLMES, et al. A Gain from Trade: From Unproductive to Prodm:- tive Entrepreneurship [ J]. Journal of Monetary Economics, 2001, 47 (2) : 417 -446.
7COE D T, HELPMAN E. International R&D Spillover.'s [ J]. Euro- pean Economic Review, 1995, 39 (5) : 859 -887.
8KELLER, WOLFGANG. Absorptive Capacity: On the Creation and Acquisition of Technology in Development [ J ]. Journal of Develop- ment Economics, 1996, 49 (1) :199-227.
9LICHTENBERG F, et al. international R&D Spillovers: A Ctmment [J]. European Economic Review, 1998 (42):1483-1491.
10FRANKEL J A, DAVID R. Does Trade Cause Growth? [J]. Ameri- can Economic Review, 1999, 89 (3) : 379 -399.