G. Corallo, J. Sackur, S. Dehaene, and M. Sigman. Psychological science : a journal of the American Psychological Society / APS, 19 (11):
1110--1117(November 2008)
J. Park, M. Schlag-Rey, and J. Schlag. Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale, 149 (4):
527--529(Apr 18, 2003)