Wolfgang Kainz, Joshua W. Guag, Stefan Benkler, Dominik Szczerba, Esra Neufeld, Victor Krauthamer, Joel Myklebust, Howard I. Bassen, Isaac A Chang, Nicolas Chavannes, Jung Hwan Kim, Malisa Sarntinoranont, and Niels Kuster, in Physics in Medicine and Biology, Volume 55, Issue 23, pp. 7253–7261, December 2010, online November 16