1. Concise report on the world population situation in 2014;United Nations Economic & Social Affairs,2014
2. World urbanization prospects: the 2014 revision;United Nations Economic & Social Affairs,2014
3. United Nations Population Fund. 2015 17-06-15. Urbanization. United Nations . 17-06-15.
4. The World Bank. 2015 18-06-15. Urban population (% of total). The World Bank . 18-06-15.
5. Common wealth: economics for a crowded planet;Sachs,2008