1. Agence France-Presse, "Beijing's Population to Hit 20 Million by 2020," October 22, 2007 http://newsinfo.inquirer.net/breakingnews/world/view_article.php?article_id=96096
2. Au, Chun-Chung and J. Vernon Henderson, "How Migration Restrictions Limit Agglomeration and Productivity in China," Journal of Development Economics , 80 , 350-388, 2006.
3. Beijing Population Census Office and Beijing Bureau of Statistics, Beijingshi 2000 nian renkou pucha ziliao (Tabulation on the 2000 Population Census of Beijing City). Beijing, China: China Statistical Press, 2002.
4. Beijing Qingnian Bao, "Renjun GDP jiangan changzhu renkou jixuan (Per Capita GDP to Be Calculated Based on the Resident Population)," Beijing Qingnian Bao (Beijing Youth News) , December 24, 2003 http://www.china.com.cn
5. Beijing University, Department of Urban and Environmental Studies, "Zhongguo chengzhen hua shuiping de xiubu he chengshi guimo fenbu yanjiu (Research on and Adjustments to China's Urbanization Level and City Size)," in State Council, Population Census Office, and Department of Population Statistics, State Statistical Bureau, eds., 2000 renkou pucha guojiya zhongdian keti yanjiu baogao (Report on National Key Research Projects on 2000 Population Census). Beijing, China: Zhongguo tongji chubanshe, 2005.