• Bulletin of the Korean Mathematical Society
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• v.41 no.2
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• pp.235-239
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• 2004

Vaughan proved that if X is countably compact, then the Alexandroff duplicate A(X) is acc. In this note, we give an example to show that the result can not be generalized to star-Lindelof spaces. Moreover, we give a positive result.

• Communications of the Korean Mathematical Society
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• v.21 no.3
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• pp.527-532
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• 2006

In this paper, we construct an example of a normal centered-Lindelof space X such that $St-l(X){\geq}{\omega}1\;under\;2^{\aleph_0}=2^{\aleph_1}$