Existence principles and a upper and lower solution theory for the one-dimension p-Laplacian singular boundary value problem with sign changing nonlinearities

The singular boundary value problem(Phi(u)) + q(t)g(t,u) = 0, 0 1, and phi is a continuous, strictly increasing odd function defined on (-infinity, +infinity). The singularity may occur at u = 0 or t = 0, and the function g may be superlinear at u = infinity and may change signs. The existence of solutions is obtained via an upper and lower solutions method and existence principles.