Srivastava, K. B., and R.B. Saxena. “On Interpolation Operators - III (A Proof of Telyakovskii-Gopengauz’s Theorem for Differentiable Functions)”. Anal. Numér. Théor. Approx. 10, no. 2 (August 1, 1981): 247–262. Accessed May 18, 2024. https://ictp.acad.ro/jnaat/journal/article/view/1981-vol10-no2-art15.