1. V. K. Dzyadyk, constructive characterization of functions satisfying the condition Lip α (0<α<1) on a finite segment of the real axis,Izv. Akad. Nauk SSSR, Ser. Mat.,20 (1956), 623–642 (in Russian).
2. I. E. Gopengauz, On a theorem of A. F. Timan on approximation of functions by polynomials on a finite interval,Mat. Zametki,1 (1967), 163–172 (in Russian).
3. G. Mastroianni and J. Szabados, Jackson order of approximation by Lagrange interpolation,Rendiconti del Circolo Matematico di Palermo,33 (1993), 375–386.
4. Xin Li, On the Lagrange interpolation for a subset ofC k functions, manuscript.