1. (1999). American Art Book. London: Phaidon Press.
2. American Mathematical Society. (2013). Mathematical imagery website. Retrieved March 13, 2013, from http://www.ams.org/mathimagery/
3. Animals in Medieval Art. (2011). Heilbrun timeline of art history. Department of Medieval Art and The Cloisters, The Metropolitan Museum of Art. Retrieved September 11, 2012, from http://www.metmuseum.org/toah/hd/best/hd_best.htm