Dragomir, Sever S., and Josip E. Pečarić. “Refinements of Some Inequalities for Isotonic Functionals”. Anal. Numér. Théor. Approx. 18, no. 1 (February 1, 1989): 61–65. Accessed April 11, 2025. https://ictp.acad.ro/jnaat/journal/article/view/1989-vol18-no1-art7.