Bashir Ahmad, et al. “Differential Equations and Inclusions Involving Mixed Fractional Derivatives With Four-Point Nonlocal Fractional Boundary Conditions”. Journal of Computational Analysis and Applications (JoCAAA), vol. 29, no. 5, Oct. 2021, pp. 817-3, https://eudoxuspress.com/index.php/pub/article/view/195.