Kostova, V. At. “Approximation of Non-Negative Convex Functions by Polynomials With Positive Coefficients in the Hausdorff Metric”. Anal. Numér. Théor. Approx. 12, no. 2 (August 1, 1983): 141–149. Accessed September 4, 2025. https://www.ictp.acad.ro/jnaat/journal/article/view/1983-vol12-no2-art5.