Multipliers of Fourier series (Q1190936)

Let \(S\) be a nonempty set of integers, and let \(C_ S(T)\) be a subspace of those \(f\) of \(C(T)\), \(T=(-\pi,\pi]\) whose spectrum is in \(S\), i.e., \(\{k:\hat f(k)\neq 0\}\subset S\). The paper deals with new propositions for multipliers of trigonometrical Fourier series in the spaces \(C(T)\) and \(C_ S(T)\).