[1] George Mason Univ, Dept Math Sci, Fairfax, VA 22030 USA
[2] George Mason Univ, Ctr Math & Artificial Intelligence CMAI, Fairfax, VA 22030 USA
[3] Chiba Univ, Grad Sch Sci & Engn, Div Math & Informat, Dept Appl & Cognit Informat,Inage Ku, 1-33 Yayoicho, Chiba, 2638522, Japan
[4] Chiba Univ, Fac Educ, Dept Math, 1-33 Yayoicho, Chiba 2638522, Japan