Balázs, M., and G. Goldner. “On Existence of Divided Differences in Linear Spaces”. Rev. Anal. Numér. Théorie Approximation 2 (February 1, 1973): 5–9. Accessed April 11, 2025. https://ictp.acad.ro/jnaat/journal/article/view/1973-vol2-art1.