Abstract
A topological space has calibre ω 1 (respectively calibre ( ω 1, ω)) if every point-countable (respectively point-finite) family of nonempty open sets is countable. An example is given in ZFC of a zero-dimensional, σ-closed-discrete Moore space with a point-countable base which has calibre ( ω 1, ω) but not calibre ω 1.
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