S. Shum, V. Uren, G. Li, B. Sereno, and C. Mancini. International Journal of Intelligent Systems (Special Issue on Computational Models of Natural Argument), 22 (1):
17-47(2007)
L. Page, S. Brin, R. Motwani, and T. Winograd. Proceedings of the 7th International World Wide Web Conference, page 161--172. Brisbane, Australia, (1998)