M. Matsuhara, K. Araki, Y. Momouchi, and K. Tochinai. Australian Joint Conference on Artificial Intelligence, volume 1747 of Lecture Notes in Computer Science, page 474-475. Springer, (1999)
M. Matsuhara, K. Araki, and K. Tochinai. Australian Joint Conference on Artificial Intelligence, volume 2557 of Lecture Notes in Computer Science, page 648-659. Springer, (2002)