R. Gacitua, P. Sawyer, and P. Rayson. Knowledge-Based Systems, 21 (3):
192 - 199(2008)AI 2007, The 27th SGAI International Conference on Artificial Intelligence.
E. Jensen, S. Beitzel, O. Frieder, and A. Chowdhury. Special interest tracks and posters of the 14th international conference on World Wide Web, page 1176--1177. New York, NY, USA, ACM, (2005)