1. Positive solutions of singular sublinear Dirichlet boundary value problems;Zhang;SIAM J. Math. Anal.,1995
2. A nonlinear singular boundary value problem;Taliaferro;Nonlinear Anal.,1979
3. Topologie et équations functionnelles;Leray;Ann. Sci. Ec. Norm. Super.,1934
4. N.G. Lloyd, Degree Theory, Cambridge Tracts in Mathematics, vol. 73, London, 1978.
5. Sur la méthode de continuité de Poincaré;Granas;C. R. Acad. Sci., Paris,1976