Crăciun, Maria. “On Compound Operators Constructed With Binomial and Sheffer Sequences”. Rev. Anal. Numér. Théor. Approx. 32, no. 2 (August 1, 2003): 135–144. Accessed March 1, 2024. https://ictp.acad.ro/jnaat/journal/article/view/2003-vol32-no2-art2.