6'Beijing’’s Per Capita GDP Surpasses $6,000 in 2006'. http://www.bj.xinhuanet.com/bjpd_sdzx/2007-01/24/content_9129211.htm .
7National Bureau of Statistics of China.'Guangzhou and Shenzhen Are Less Urbanized than Beijingand Shanghai'. http://news.21cn.com/domestic/yaowen/2007/10/05/3657058.shtml .
8Bureau of Statistics of Beijing.Beijing Statistical Yearbook 2006. http://www.bjstats.gov.cn/tjnj/2006-tjnj/ .