On the nonexistence of limit cycle for a type of plane differential system LI Jian—quan,YANG You～she (Telecommunication Engineering Institute，Air Force Engineering Un[versity，Xi’an 710077，China)  全文: PDF   摘要： 关键词： differential systems；singular points；limit cycles}nonexistence 发表年限: 2003年 发表期号: 第2期