中国科学院数学与系统科学研究院期刊网
On the Existence of Periodic Solutions for a Kind of Second Order n-Dimensional Neutral Differential Systems
Shi Ping LU(1),Wei Gao GE(2)
Acta Mathematica Sinica, Chinese Series . 2003, (3): 601 -610 .  DOI: 10.12386/A2003sxxb0082