[1] Tech Univ Denmark, Dept Math & Comp Sci, Lyngby, Denmark
[2] Nanjing Univ Aeronaut & Astronaut, Nanjing, Jiangsu, Peoples R China
[3] Univ Waterloo, Waterloo, ON, Canada
[4] Univ Salerno, Fisciano, Italy
[5] Univ Naples Federico II, Naples, Italy
[6] Hong Kong Polytech Univ, Hong Kong, Hong Kong, Peoples R China