1. Abel, U.: Asymptotic approximation by de la Vallée Poussin means and their derivatives. J. Approx. Theory 126(2), 115–125 (2004)
2. Bleimann, G., Stark, E.L.: A trigonometric version of Taylor’s formula. In: Ciesielski, Z. (ed.) Proceedings of the International Conference on Approximation and Function Spaces, Gdansk 1979, pp. 149–162. North-Holland, Amsterdam (1981)
3. Butzer, P.L., Nessel, R.J.: Fourier Analysis and Approximation, vol. 1. Academic Press, New York (1971)
4. Butzer, P.L., Schmidt, M., Stark, E.L., Vogt, L.: Central factorial numbers; their main properties and some applications. Numer. Funct. Anal. Optim. 10(5–6), 419–488 (1989)
5. Komleva, E.A.: About asymptotic properties of positive summation methods of Fourier series (in Russian). Izv. vyss. ucebn. zaved. math. 4(11), 89–93 (1959)