Pew Research Center, May 2011, updated September 2018, "Beyond Red vs. Blue: The Political Typology".

Pew Research Center, January 2011, "The Future of the Global Muslim Population".

Pew Research Center, December 2011, "Global Christianity – A Report on the Size and Distribution of the World’s Christian Population".

Pew Research Center, April 2010, "Tolerance and Tension: Islam and Christianity in Sub-Saharan Africa".

Pew Research Center, September 2010, "U.S. Religious Knowledge Survey".