Fred S. Kleiner and Christin J. Mamiya, Gardner's Art Through the Ages, 12th ed., vol 2 (Belmont, CA: Thomson/Wadsworth, 2005), 743-44; Encyclopædia Britannica, 2006 Online ed., s.v. “Neumann, Balthasar”, available from Internet <http://search.eb.com.erl.lib.byu.edu/eb/article-9055370>, accessed 15 February 2008;