Existence of three non-negative solutions for a three-point boundary-value problem of nonlinear fractional differential equations

This article concerns the existence of three non-negative solutions for two kinds of three-point boundary-value problems of nonlinear fractional differential equations, where the fractional derivative is taken in the Riemann-Liouville sense. Using Leggett-Williams fixed point theorem, we present some existence criteria and then illustrate our results with examples