中国科学院数学与系统科学研究院期刊网
EXISTENCE OF PERIODIC SOLUTION FOR NONLINEAR NEUTRAL DELAY DIFFERENTIAL EQUATION
Jing Li REN, Xian Bao REN, Wei Gao GE
Acta Mathematicae Applicatae Sinica . 2004, (1): 89 -98 .  DOI: 10.12387/C2004010