Email:
weigu@math.pku.edu.cn (Prof. Weigu Li) or
sunwx@math.pku.edu.cn (Prof. Wenxiang Sun)
Fax: 0086 -10 - 62751801
Mailling Address:
Professor Weigu Li or Professor Wenxiang Sun School of Mathematical Sciences Peking University Beijing 100871 P.R. China
