6Delong J B, Lawrence H S. Equipment Investment and Economic Growth: How Robust is the Nexus?[M]. Brookings Papers on Economic Activity, 1992: 155-199.
7Delong J B, Summers L H. Equipment Investment and Economic Growth[J]. Journal of Economics, 1992 (2) : 445-502.
8Levine R, Renelt D. A Sensitivity Analysis of Cross Country Growth Regressions[J]. American Economic Review, 1992 (2): 942-63.