Kolmogorov's type criteria for spaces of compact operators (Q1174317)

The author gives various theorems on Kolmogorov's type criteria for spaces of compact operators and proves several results concerning strongly unique best approximation. The characterisations are expressed in a form which is more convenient for applications. Indeed some classical results from the theory of minimal projections due to Cheney and others: (i) \textit{E. W. Cheney} and \textit{K. Price} [ Iterationsverf., Numer. Math., Approximationstheorie, Oberwolfach 1968 u. 1969, 115--121 (1970; Zbl 0217.16201)], (ii) \textit{E. W. Cheney}, \textit{P. D. Moris} and \textit{K. H. Price} [J. Approximation Theory 13, 375--391 (1975; Zbl 0312.41010)], (iii) \textit{E. W. Cheney} and \textit{C. Franchetti} [Colloq. Math. Soc. János Bolyai 19, 241--253 (1978; Zbl 0421.46004)], are generalised and improved upon.