中国科学院数学与系统科学研究院期刊网
On the Uniqueness of Limit Cycle of the General Lienard Equation
Ping Guang ZHANG, Shen Qi ZHAO
Acta Mathematica Sinica, Chinese Series . 2004, (6): 1193 -120 .  DOI: 10.12386/A2004sxxb0148