Affiliation: | Li Wei 1,Hai-yun Zhou 2,Ravi P. Agarwal 3 1 School of Mathematics and Statistics,Hebei University of Economics and Business,Shijiazhuang 050061,China2 Institute of Applied Mathematics,Ordnance Engineering College,Shijiazhuang 050003,China 3 Department of Mathematical Sciences,Florida Institute of Technology,Melbourne,FL 32901,U.S.A. |