Babenko, V. F., and A. A. Ligun. “Some Bernstein-Type Inequalities for Trigonometric Polynomials”. Ukrains’kyi Matematychnyi Zhurnal 45, no. 3 (March 25, 1993): 428–430. Accessed April 11, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/5825.