1. College of Computer Science and Technology, Jilin University, Changchun, Jilin, PR China
2. Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education, Jilin University, Changchun, Jilin, PR China
3. College of Computer Science and Technology, Inner Mongolia University for Nationalities, Tongliao, Inner Mongolia, PR China
4. College of Mathematics and Physics, Inner Mongolia University for Nationalities, Tongliao, Inner Mongolia, PR China