[1]  Lan K, Webb J L. Positive solutions of semilinear differential equations with singularities. J Diff Eqns, 1998, 148: 407--421

[2]  Agarwal R P, O'regan D. A note on existence of nonnegative solutions to singular semipositone problem. Nonlinear Anal, 1999, 36: 615--622

[3]  Liu Y. Twin solutions to singular semipositone problems. J Math Anal Appl,  2003, 286: 248--260

[4]  Liu X, Yan B. Boundary-irregular solutions to singular boundary value problems. Nonlinear Anal, 1998, 3: 633--646

[5]  Xu X. On Some Results of Singular Boundary Value Problems
[D]. Jinan: Shandong University,  2001

[6]  Anuradha V, Hai D D, Shivaji R. Existence results for superlinear semipositon BVP's. Proc Amer Math Soc, 1994, 120: 743--748

[7]  Anderson D. Multiple positive solution for a three-point boundary value problem. Math Lomput Modeling, 1998, 27: 49--57

[8]  Yao Q. Existence of positive solutions for a third-order three-point boundary value problem with semipositone nonlinearity. Journal of Mathematical Research \& Exposition, 2003, 23: 591--596

[9]  Guo D, Lakshmikantham V. Nonlinear Problems in Abstract Cones. New York: Academic Press, 1988

[10]  Sun J, Liu Y. Multiple positive solutions of singular third-order periodic boundary value problem. Acta Mathematica Scientia, 2005, 25: 81--89