7Zu Li, Jing Daqing, Donal O'Regan. Existence theory for multiple solutions to semipositone Dirichlet boundary value problems with singular dependent nonlinearities for second-order impulsive differential equations[J]. Appl Math Comput, 2008, 195: 240-255.
8Sun Jianping, Li Wantong. Multiple positive solutions to second-order Neumann boundary value problems[J]. Appl Math Comput, 2003, 146: 187-194.
9Guo Dajun, Lakshmikantham V. Nonlinear Problems in Abstract Cones[M]. San Diego: Academic Press, 1988.
10Dalmasso R., Positive solutions of singular boundary value problems, Nonlinear Analysis, 1996, 27: 645-652.
