1. Bardaro, C., Musielak, J., Vinti, G.: Modular estimates and modular convergence for a class of nonlinear operators. Math. Japon. 39, 7–14 (1994)
2. Bardaro, C., Musielak, J., Vinti, G.: Approximation by nonlinear integral operators in some modular function spaces. Ann. Polon. Math. 63, 173–182 (1996)
3. Bojanić, R., Cheng, F.: Estimates for the rate of approximation of functions of bounded variation by Hermite-Fejér polynomials. In: Ditzian, Z. et al. (eds.): Second Edmonton conference on approximation theory. Providence, RI: Amer. Math. Soc. 1983, pp. 5–17
4. Bojanić, R., Vuilleumier: On the rate of convergence of Fourier-Legendre series of functions of bounded variation. J. Approx. Theory 31, 67–79 (1981)
5. Butzer, P.L., Nessel, R.J.: Fourier analysis and approximation. Vol.1: One-dimensional theory. New York: Academic Press 1971