Full Text Article Available at:
http://www.sciencedirect.com/science/article/B6WKD-4T0805P-1/2/3e098ffed59c40...
Author: Guodong Liu, PhD
Dept. of Mathematics
Huizhou University
Huizhou, Guangdong, 516015
P. R. China
E-mail:gdliu@pub.huizhou.gd.cn
Manuscript Number: JNT-D-08-00083R1
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