中国科学院数学与系统科学研究院期刊网
STUDY ON THE POINCARE BIFURCATION OF QUADRATIC SYSTEM WITH TWO CENTERS AND TWO UNBOUNDED HETEROCLINIC LOOPS ONCE AGAIN
Xin Xin TAN, En Min FENG, Bo Qian SHEN
Acta Mathematicae Applicatae Sinica . 2004, (2): 300 -309 .  DOI: 10.12387/C2004035