8Au, C. C. , Henderson, J. V. , Are Chine Cities Too Small? The Review of Economic Studies, Vol. 73, 2006, pp. 549--576.
9Barro, R. J. , Sala-i-Martin, X. , Blanchard, O. J. , Hall, R. E. , Convergence across States and Regions. Brookings Papers on Economic Activity, Vol. 1,1991, pp. 107-- ] 82.
10Beeson, P. E. , DeJong, D. N. , Troesken, W. , Population Growth in US Counties, 1840-- 1990. Regional Science and Urban Economics, Vol. 31, 2001, pp. 669--699.