Department of Mathematics and Information Science, Zhangzhou Normal University, Zhangzhou 363000, China; Department of Mathematics, Shangqiu Teacher's College, Shangqiu 476000, China
About author:LIKedian(1956-),male,native of Zhecheng,Henan,a professor of Zhangzhou Normal Univer- sity,engages in general topology.
Supported by:
Foundation item: Supported by the NSF of Fujian(Z0511033) Supported by the Eduction Committee of Fujian(JB04298) Supported by the Eduction Committee of Henan (2004606018, 200510483002)；
