Butzer, Paul L.; Nessel, R. J.; Trebels, Walter On summation processes of Fourier expansions in Banach spaces. III: Jackson- and Zamansky-type inequalities for Abel-bounded expansions. (English) Zbl 0324.42004 Tohoku Math. J., II. Ser. 27, 213-223 (1975). MSC: 42A45 41A65 42C10 42C15 PDFBibTeX XMLCite \textit{P. L. Butzer} et al., Tôhoku Math. J. (2) 27, 213--223 (1975; Zbl 0324.42004) Full Text: DOI
Görlich, E.; Nessel, R. J.; Trebels, Walter Zur Approximationstheorie für Summationsprozesse von Fourier- Entwicklungen in Banach-Räumen: Vergleichssätze und Ungleichungen vom Bernstein-Typ. (German) Zbl 0305.41025 Approx. Theor., Proc. Conf. Poznan 1972, 87-96 (1975). MSC: 41A65 42A45 42C05 42C10 PDFBibTeX XML
Trebels, Walter Multipliers for (C,a)-bounded Fourier expansions in Banach spaces and approximation theory. (English) Zbl 0293.41035 Lecture Notes in Mathematics. 329. Berlin-Heidelberg-New York: Springer-Verlag. VII, 103 p. DM 16.00; $ 6.00 (1973). MSC: 41A65 42A45 41-02 42-02 41A25 40J05 26A33 PDFBibTeX XML
Butzer, Paul L.; Nessel, R. J.; Trebels, Walter Multipliers with respect to spectral measures in Banach spaces and approximation. I: Radial multipliers in connection with Riesz-bounded spectral measures. (English) Zbl 0268.41019 J. Approximation Theory 8, 335-356 (1973). MSC: 41A65 41A25 41A63 42A45 47B15 PDFBibTeX XMLCite \textit{P. L. Butzer} et al., J. Approx. Theory 8, 335--356 (1973; Zbl 0268.41019) Full Text: DOI
Butzer, Paul L.; Nessel, R. J.; Trebels, Walter On the comparison of approximation processes in Hilbert spaces. (English) Zbl 0253.41025 Linear Operators Approximation, Proc. Conf. Oberwolfach 1971, ISNM 20, 234-253 (1972). MSC: 41A65 47B15 41A25 42A45 42C15 42A24 42A38 42A75 PDFBibTeX XML
Butzer, Paul L.; Nessel, R. J.; Trebels, Walter On summation processes of Fourier expansions in Banach spaces. I: Comparison theorems. (English) Zbl 0242.42016 Tohoku Math. J., II. Ser. 24, 127-140 (1972). MSC: 42C15 41A65 42A45 41A25 40D15 42A65 PDFBibTeX XMLCite \textit{P. L. Butzer} et al., Tôhoku Math. J. (2) 24, 127--140 (1972; Zbl 0242.42016) Full Text: DOI