Dragomir, S.S. and Khan, L. 2004. Two discrete inequalities of Gr"uss type via P’olya-Szeg"o and Shisha-Mond results for real numbers. Tamkang Journal of Mathematics. 35, 2 (Jun. 2004), 117–128. DOI:https://doi.org/10.5556/j.tkjm.35.2004.213.