Gavrea, I., and I. Rașa. “Remarks on Some Quantitative Korovkin-Type Results”. Rev. Anal. Numér. Théor. Approx. 22, no. 2 (August 1, 1993): 173–176. Accessed April 26, 2024. https://ictp.acad.ro/jnaat/journal/article/view/1993-vol22-no2-art6.