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Hurewicz scheme. (English) Zbl 1177.03049

Summary: We present a simple proof of Hurewicz theorem saying that every coanalytic non-\(G_\delta\)-set \(C\) in a Polish space contains a countable set \(L\subseteq C\) without isolated points such that \((\overline{L}\setminus L)\cap C=\emptyset\).

MSC:

03E15 Descriptive set theory
42A20 Convergence and absolute convergence of Fourier and trigonometric series
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