Catholic Encyclopedia. New York: Robert Appleton Company. ↑ St. Peter's in the Vatican edited by William Tronzo, pgs 83-85 ↑ Signs and Symbols in Christian Art by G. Ferguson ↑ Florence edited by Gene A. Brucker, pg 46 ↑ The Grove Encyclopedia of Decorative Arts, Volume 2 edited by Gordon Campbell, pg 204 ↑ Art and Architecture in Italy, 1600-1750, Volume 3 by Rudolf Wittkower, pgs 88-89 ↑ The Glory of Venice edited by Jane Martineau and Andrew Robison, pg 473 ↑ The Grove Encyclopedia of Decorative Arts, Volume 2 edited by Gordon Campbell, pgs 211-212 ↑ Herbermann, Charles, ed. (1913).