"Popes since AD 1000." World Encyclopedia. 2005. Encyclopedia.com. 22 Nov. 2009 <http://www.encyclopedia.com>.
"Popes since AD 1000." World Encyclopedia. 2005. Encyclopedia.com. (November 22, 2009). http://www.encyclopedia.com/doc/1O142-PopessinceAD1000.html
"Popes since AD 1000." World Encyclopedia. 2005. Retrieved November 22, 2009 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-PopessinceAD1000.html