2Coe, David T. and Elhanan Helpman, International R&D Spillovers [J], European Economic Review, May 1995, 39, 859-887.
3Engle, Robert F. and Granger Clive W. J. Cointegration and Error Correction, Representation, Estirnationand Testing [J], Econometrica, March 1987, 55, 251-276.
4Granger, Clive W. J. , Developments in the Study of Cointegrated Economic Variables [J], Oxford Bulletin of Economics and Statistics, August 1986, 48, 213-233.