Proceedings of the 12th conferenc of the IAMG International Association for Mathematical Geology, 26-31 August, 2007, Beijing, China. pp. 421-424, 421-424 STARTPAGE=421;ENDPAGE=424;TITLE=Proceedings of the 12th conferenc of the IAMG International Association for Mathematical Geology, 26-31 August, 2007, Beijing, China. pp. 421-424