数学物理学报 ›› 1999, Vol. 19 ›› Issue (4): 379-386.
(江苏理工大学数学系 |镇江 212013) (福建林学院基础系 |福建 353001)
(Jiangsu Univerrsity of Science &|Technology, Zhenjiang, Jiangsu, 212013)
(Fujian Forestry Instiute, Nanpin, Fujian, 353001)
(Shanghai University, Shanghai, 201800)