An Unpublished Result of P. \v Sleich: Sets of Type H(s) are σ-bilaterally porous

Abstract

The sets of type $H^{(s)}$ form an important subclass of the class of sets of uniqueness ($U$-sets) for trigonometrical series. The main aim of this note is to present a proof of an unpublished result of P. \v Sleich which asserts that each set of type $H^{(s)}$ is $\sigma$-bilaterally porous.