How much land is needed to power the world’s major cities by solar?

http://www.pennenergy.com/articles/pennenergy/2017/09/how-much-land-is-needed-to-power-the-world-s-major-cities-by-solar-power.html?cmpid=enl_pennenergy_pennenergy_weekly_power_updates_2017-09-08&email_address=micheletkearney@gmail.com&eid=288118515&bid=1859891