ChenF. X. “On the Generalization of Some Hermite – Hadamard Inequalities for Functions With Convex Absolute Values of the Second Derivatives via Fractional Integrals”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 70, no. 12, Dec. 2018, pp. 1696-0, https://umj.imath.kiev.ua/index.php/umj/article/view/1668.