8BARRY R. 1999. Chiswick are immigrants favorably self- selected[ J]. American Economic Review,5 : 181-185.
9FAN C, ZHENG S. 2011. Migration and Split Households: A Comparison of Sole, Couple and Family Migrants in Beijing, China [ J ]. Environment and Planning A, 43 (9) : 2164-2185.
10SJAASTAD L. 1962. The costs and returns of human migration [ J ] .Journal of Political Economy, 70 : 80-93.