Pew Research Center, May 2011, updated June 2014, October 2017, and November 2021; “Beyond Red vs. Blue: The Political Typology”.

Pew Research Center’s Forum on Religion & Public Life, January 2011, “The Future of the Global Muslim Population: Projections for 2010 - 2030”.

Pew Research Center’s Forum on Religion & Public Life, April 2010, “Tolerance and Tension: Islam and Christianity in Sub-Saharan Africa”.

Pew Research Center’s Forum on Religion & Public Life, September 2010, “U.S. Religious Knowledge Survey”.