1. Inverse theorems for Bernstein polynomials;Berens;Indiana Univ. Math. J.,1972
2. Quadraturverfahren;Brass,1977
3. The Banach-Steinhaus theorem with rates and applications to various branches of analysis;Butzer,1980
4. Semi-Groups of Operators and Approximation;Butzer,1967
5. Fourier Analysis and Approximation, I;Butzer,1971