van Iperen, H.; Sikkema, P. C. Determination of a class of best constants in the approximation by powers of generalized Bernstein operators. (English) Zbl 0164.07003 Nederl. Akad. Wet., Proc., Ser. A 71, 336-352 (1968). PDFBibTeX XMLCite \textit{H. van Iperen} and \textit{P. C. Sikkema}, Nederl. Akad. Wet., Proc., Ser. A 71, 336--352 (1968; Zbl 0164.07003)
van Iperen, H. A theorem about the determination of a certain best constant in the approximation by some linear operators. (English) Zbl 0164.07002 Nederl. Akad. Wet., Proc., Ser. A 71, 303-311 (1968). PDFBibTeX XMLCite \textit{H. van Iperen}, Nederl. Akad. Wet., Proc., Ser. A 71, 303--311 (1968; Zbl 0164.07002)