Published online by Cambridge University Press: 20 November 2018
In [1], Willard proves the following
If a regular paracompact space X has a dense Lindelöfsubspace, then X is Lindelöf.
Willard notes that the above is a generalization of the standard theorem: A separable paracompact space is Lindelöf. Actually, it is a standard fact ([2, p. 24]) that a separable metacompact space is Lindelöf. Moreover, one discovers that if a separable space X is such that each open cover of X has a point-countable open refinement, then X is Lindelöf.