On Certain Onto Maps

Abstract
Let Δn (n > 0) denote the subset of the Euclidean (n + 1)-dimensional space defined by A subset σ of Δn is called a face if there exists a sequence 0 ≤ i1 ≤ i2< im ≤ n such that and the dimension of σ is defined to be (n — m). Let denote the union of all faces of Δn of dimensions less than n. A topological space Y is called solid if any continuous map on a closed subspace A of a normal space X into Y can be extended to a map on X into Y. By Tietz's extension theorem, each face of Δn is solid. The present paper is concerned with a generalization of the following theorem which seems well known.

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