On the Variational Characterization of Bivariate Interpolation Methods.
On the Yosida approximation and the Widder-Arendt representation theorem
The Yosida approximation is treated as an inversion formula for the Laplace transform.
On Typical Compact Convex Sets in Hilbert Spaces
Let E be an infinite dimensional separable space and for e ∈ E and X a nonempty compact convex subset of E, let qX(e) be the metric antiprojection of e on X. Let n ≥ 2 be an arbitrary integer. It is shown that for a typical (in the sence of the Baire category) compact convex set X ⊂ E the metric antiprojection qX(e) has cardinality at least n for every e in a dense subset of E.
On uniform approximation of bounded approximately continuous functions by differences of lower semicontinuous and approximately continuous ones
On upper semicontinuity in good coapproximation
On weak Chebyshev subspaces and Chebyshev approximation by their elements
On -suns
Optimal and Sard approximation
Optimal Approximation and Error Bounds in Seminormed Spaces.
Optimal Nodes for Interpolation in Hardy Spaces.
Optimal reconstruction of derivatives on the Sobolev classes.
Optimal recovery of analytic functions by their values in a uniform grid on a circle.
Optimal universal approximations of Fourier coefficients in spaces of continuous periodic functions
Optimale Approximation linearer Funktionale auf periodischen Funktionen.
Optimale Approximation mit Nebenbedingungen an lineare Funktionale auf periodischen Funktionen. - Optimal Approximation with Side Conditions to Linear Functionals on Periodic Functions.
Orthogonality in normed linear spaces. A survey I: Main properties.
Perturbations of Best Approximation Problems.
Polynomial approximation of differentiable functions on Banach spaces.
Polynomial approximations and universality
We give another version of the recently developed abstract theory of universal series to exhibit a necessary and sufficient condition of polynomial approximation type for the existence of universal elements. This certainly covers the case of simultaneous approximation with a sequence of continuous linear mappings. In the case of a sequence of unbounded operators the same condition ensures existence and density of universal elements. Several known results, stronger statements or new results can be...
Polynomials and multilinear mappings in topological vector-spaces