Last-modified: 2010-07-22 (木) 14:46:01
Suppose that if U is an open cover of a topological space X, there exests a sequence of open covers and for every point x in X, there exists an index m and W in U such that .
Dennis K. Burke, On subcompact spaces, Proc. Amer. Math. Soc. Vol.23 No.3 (1969) pp.655-663.