Saxena, R.B., and K. B. Srivastava. “On Interpolation Operators (II) (A Proof of Timan’s Theorem for Differentiable Functions)”. Anal. Numér. Théor. Approx. 8, no. 2 (August 1, 1979): 215–227. Accessed November 23, 2024. https://ictp.acad.ro/jnaat/journal/article/view/1979-vol8-no2-art12.