Dragomir, S. S., and A. Sofo. “An Integral Inequality for Twice Differentiable Mappings and Applications”. Tamkang Journal of Mathematics 31, no. 4 (December 31, 2000): 257-266. Accessed July 25, 2021. https://journals.math.tku.edu.tw/index.php/TKJM/article/view/382.