1. R. D. Getsadze, Problem of N.Kirchhoff and R.Nessel.J. Approx. Theory (to appear).
2. N. Kirchhoff and R. J. Nessel, Divergence almost everywhere of a pointwise comparison of trigonometric convolution process with their discrete analogues.J. Approx. Theory 1(1992), 29–38.
3. S. M. Lozinski, On an analogy between the summation of Fourier series and that of interpolation trigonometric polynomials.C. R. Acad. Sci. URSS (N.S.) 39(1943), 83–97.
4. S. Lozinski, On convergence and summability of Fourier series and interpolation processes.Mat. Sb. 14(56)(1944), No. 3, 175–268.
5. N.K. Bari, A Treatise on Trigonometric Series, Vols. 1 and 2. Pergamon, New York, 1964. Russian original: Fizmatgiz, Moscow, 1961.