Retrieved 2010-09-01. ↑ http://www.demographia.com/db-megacity.pdf ↑ http://www.demographia.com/db-worldua.pdf ↑ http://www.espon.eu/export/sites/default/Documents/Projects/ESPON2006Projects/StudiesScientificSupportProjects/UrbanFunctions/fr-1.4.3_April2007-final.pdf ↑ "p.