How Many People are in Tahir Square? Here's How to Tell - Wired, Feb. 1, 2011
The Madness of Estimating Crowds !and Commodes - Wall St. Journal, Jan. 9, 2009
Inauguration Turnout of People and Port-a-Potties Could be a Record, But No One Knows; Keep Off My 5 Square Feet
Why is it so hard to estimate crowd size? - AOL News, Aug. 30, 2010