Hua Ying WEI Wuhan Institute of Physics and Mathematics,Chinese Academy of Sciences,Wuhan 430071,P.R.China Qiao Hua YANG School of Mathematics and Statistics,Wuhan University,Wuhan 430072,P.R.China
Acta Mathematica Sinica, Chinese Series
.
2009, (01): 83
-92
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DOI: 10.12386/A2009sxxb0008
