1. Iteration of positive approximation operators;Karlin;J. Approximation Theory,1970
2. Iterates of Bernstein polynomials;Kelisky;Pacific J. Math.,1967
3. Bernstein Polynomials;Lorentz,1953
4. Saturation Classes and Iterates of Operators;Micchelli,1969
5. Sätze Korovkinschen Typs für die Approximation linearer positiver Operatoren;Nagel,1978