Caballero, J., J. Harjani, B. López, and K. Sadarangani. “Existence of Positive Solutions in the Space of Hölder Functions for a Class of Nonlinear Fractional Differential Equations With Integral Boundary Conditions”. Topological Methods in Nonlinear Analysis, vol. 63, no. 1, Mar. 2024, pp. 185-96, doi:10.12775/TMNA.2023.038.