Stancu, D. D., & Occorsio, M. R. (1998). On approximation by binomial operators of Tiberiu Popoviciu type. Rev. Anal. Numér. Théor. Approx., 27(1), 167-181. https://ictp.acad.ro/jnaat/journal/article/view/1998-vol27-no1-art17