1. Über Summierbarkeit von Orthogonalentwicklungen stetiger Funktionen;Aljancic;Acad. Serbe Sci. Publ. Inst. Math.,1956
2. On uniform convergence of Fourier series;Bojanic;Acad. Serbe Sci. Publ. Inst. Math.,1956
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. On Jackson-type inequalities in approximation theory;Butzer,1978