G. Sim, P. Holifield, and M. Brown. ALT-J, Research in Learning Technology, (September 2004)ISSN 0968�7769 (print)/ISSN 1741�1629 (online)/04/030217�15.
Y. Miao, H. Vogten, H. Martens, and R. Koper. Proceedings of the 10th IASTED International Conference on Advanced
Technologies in Education (CATE 2007), Beijing, China, ISBN: 978-0-88986-699-7.(October 2007)