Stancu, D. D., and A. Vernescu. “On Some Remarkable Positive Polynomial Operators of Approximation”. Rev. Anal. Numér. Théor. Approx. 28, no. 1 (February 1, 1999): 85–95. Accessed May 19, 2024. https://ictp.acad.ro/jnaat/journal/article/view/1999-vol28-no1-art8.