Goldner, G. “On the Divided Differences and Fréchet Derivatives”. Rev. Anal. Numér. Théorie Approximation 3, no. 1 (February 1, 1974): 33–36. Accessed April 11, 2025. https://ictp.acad.ro/jnaat/journal/article/view/1974-vol3-no1-art5.