7Allyn Young, Increasing Returns and Economic Progress, The Economic Journal, 38 : 527 -542, 1928.
8David B. Audretsch and Maryann P. Feldman, R&D spillovers and the Geography of Innovation and Production,America Economic Review, 86 (3) : 631 -640, 1996.
9Gordon H. Hanson. Scale Economies and the Geographic Concentration of Industry, NBER Working paper ,No. 8013, 2000.
10Hubert Schmitz and Khalid Nadvi, Clustering and Industrialization: Introduction, World Development, 27 ( 9 ) :1503 - 1514, 1999.