8Vania S, Dolores A H. Productivity, R&D spillovers and educational attainment[J]. Oxford Bulletin of Eco- nomics and Statistics, 2014(76):1-23.
9Omri A.CO emissions, energy consumption and eco- nomic growth nexus in MENA countries: Evidence from simultaneous equations models[J]. Energy Economics, 2013(40):657-664.
10Feldstein M. How to achieve stronger US growth[J]. Journal of Policy Modeling, 2014(36):649-653.