中国科学院数学与系统科学研究院期刊网
AMS
Periodic Solutions of Singular Second Order Equations at Resonance
Yin Yin WU, Ding Bian QIAN
Acta Mathematica Sinica . 2015, (10): 1599 -1610 .  DOI: 10.1007/s10114-015-4596-7