Jun Fang ZHAO Department of Mathematics,Beijing Institute of Technology,Beijing 100081,P.R.China Wen Li WANG Faculty of Information Engineering,China University of Geosciences Great Wall College, Baoding 071000,P.R.China Wei Gao GE Department of Mathemati
Acta Mathematica Sinica, Chinese Series
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2009, (02): 53
-62
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DOI: 10.12386/A2009sxxb0031