9CULLEN, JULIE BERRY, ROGER H GORDON. Taxes and entre- preneurial activity: Theory and evidence for the U. S. [ C ]. NBER Working Paper No. 9015, 2002.
10DAVID P A, HALL B H, TOOLE A A. Is public R&D a comple- ment or substitute for private R&D? A review of the econometric evi- dence [ J]. Research Policy, Oorganizations - CIRANO, Discussion Paper, 1997 (4): 97-34.