8Dall'erba S,Le Gallo J.Regional convergence and the impact of European structural funds over 1989-1999:A spatial econometric analysis.Regional Science,2008,87(2):219-244.
9Fingleton B,McCombie J S L.Increasing returns and economic growth:Some evidence for manufacturing from the European Union regions.Oxford Economic Papers,1998,50:89-105.
10Romer P M.Increasing returns and long-ran growth.Journal of political Economics,1986,94(5):1002-1037.