Covers and envelopes were de ned in 11] and the same notions (but with the terminology
right and left minimal approximations) were de ned in 4]. In this article we will give some of …

Covering Spaces may be studied from several points of view and with respect to many kinds
of spaces. The earliest form of covering spaces considered was that of the Riemann surface …

Abstract In [1], we study coverings in the setting of directed topology. Unfortunately, there is a
condition missing in the definition of a directed covering. Some of the results in [1] require …

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Covering spaces revisited Page 1 ROCZNIKI POLSKIEGO TOWARZYSTWA MATEMATYCZNE
GO Séria I: PEACE MATEMATYCZNE XV (1971) ANNALES SOCIETATIS MATHEMATICAE …

In [7](pg. 207) a theorem was given guaranteeing the existence of certain kinds of covers. A
dual theorem proves the existence of envelopes. These theorems do not prove the existence …

Publisher Summary For a set S, a family of subsets of S is called a cover if the union⋃{A:
A∈} is S. A cover C of S is called finite if the cardinality of C is finite. For two covers B and C …

Definition 1.1 A covering projection is a continuous surjection p: ̂X→ X such that for each
x∈ X, there is an open set U⊆ op X containing x that is evenly covered by p in the sense …

Introduction. The classical theory of covering spaces treated onlyconnected and locally
connected spaces (eg,[1],[2]). Novosad recently introduced new definitions of covering …