1. Department of Computer Science, Kennesaw State University, Marietta, GA 30060, USA
2. Department of Mathematics and Computer Science, California State University, East Bay, Hayward, CA 94542, USA
3. Department of Mathematics and Physics, North Carolina Central University, Durham, NC 27707, USA
4. Key Laboratory of Data Engineering and Knowledge Engineering (Renmin University), MOE School of Information, Renmin University of China, P. R. China
5. Department of Computer Science, Georgia State University, Atlanta, GA 30303, USA