Gonska, H., and R. Păltănea. “Quantitative Convergence Theorems for a Class of Bernstein–Durrmeyer Operators Preserving Linear Functions”. Ukrains’kyi Matematychnyi Zhurnal 62, no. 7 (July 25, 2010): 913–922. Accessed April 23, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/2924.