The Huarochiri manuscript : a testament of ancient and Colonial Andean
    religion.  Austin : University of Texas Press, 1991.

Cobo, Bernabe.  Inca religion and customs.  Austin, TX : University of Texas Press, 1990.

Conrad, Geoffrey W.  Religion and empire : the dynamics of Aztec and Inca expansionism.
         London: Cambridge University Press, 1984.

Mason, J. Alden.  Ancient Civilizations of Peru.  London: Penguin Books. 1991.

Prater, Donna.  "Incan Religion." n.d. http://www.interpres.cz/worag/cosmol/tawan.html

Wallace, Anthony. "The Religion of  Qosqo."
        http://www.bestweb.net/~goyzueta/qosqo/religion.htm

Picture credits:

("Deities")
Viracocha:          http://www.raingod.com/angus/gallery
Apu Inti:             http://www.astronomy.com
Chiqui Illapa:      http://www.astronomy.com
Mamaquilla:       http://www.astronomy.com
Yakumama:       http://www.excite.com/pics/earth
Mamacocha :     http://www.excite.com/pics/earth
Pachakama:       http://www.usws.com
Waca:               http://www.astronomy.com

("Cosmology")
Apu Inti idol:    http://www.raingod.com

("Overview")
Landscape:    http://raingod.com/angus/Gallery/Photos/SouthAmerica/Peru/IncaTrail/Index.html
Soldiers:        http://emuseum.mankato.msus.edu/prehistory/latinamerica/topics/spanish_conquest.html

("Rituals")
Mummies:      http://www.pbs.org/wgbh/nova/peru/mummies/