R. Kumar, J. Novak, and A. Tomkins. KDD '06: Proceedings of the 12th ACM SIGKDD international conference on Knowledge discovery and data mining, page 611--617. New York, NY, USA, ACM, (2006)
L. Steels, and P. Wellens. Symbol Grounding and Beyond: Proceedings of the Third International Workshop on the Emergence and Evolution of Linguistic Communication, page 76-88. Springer, (2006)