Existence and Localization of Solution for Second Order Elliptic BVP in Presence of Lower and Upper Solutions without Any Order

We prove an existence and localization result for a solution of a second order elliptic equations with Dirichlet and regular oblique derivative boundary conditions. The main result is obtained assuming the existence of a lower and an upper solution without particular order and a positively homogeneous asymptotic behaviour of the right hand member of the equation.