R. Aviv, Z. Erlich, and G. Ravid. The 3rd IEEE International Conference on Advanced Learning Technologies, 2003. Proceedings, page 145 -- 149. (July 2003)
N. Mabrouk, G. Deffuant, and C. Lobry. Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, Genova, Italy, (9-13 July 2007)