Zhang, X (Reprint Author), South China Normal Univ, Sch Math Sci, Guangzhou 510631, Guangdong, Peoples R China.
Zhang, Xia; Ma, Wen, South China Normal Univ, Sch Math Sci, Guangzhou 510631, Guangdong, Peoples R China.
Rump, Wolfgang, Univ Stuttgart, Inst Algebra & Number Theory, Pfaffenwaldring 57, D-70550 Stuttgart, Germany.