A necessary and sufficient condition for the existence of positive solutions to singular boundary-value problems of higher order differential equations. Zhao, Chenglong; Yuan, Yanyan; Liu, Yansheng — 2006 Electronic Journal of Differential Equations (EJDE) [electronic only]
Positive solutions for systems of nonlinear singular differential equations. Yuan, Yanyan; Zhao, Chenglong; Liu, Yansheng — 2008 Electronic Journal of Differential Equations (EJDE) [electronic only]