Deng, J., et al. “Hermite-Hadamard-Type Inequalities for R-Convex Functions Using Riemann-Liouville Fractional Integrals”. Ukrains’kyi Matematychnyi Zhurnal, vol. 65, no. 2, Feb. 2013, pp. 175-91, https://umj.imath.kiev.ua/index.php/umj/article/view/2412.