Alexey Ostrovsky
Published 2011-02-09, updated 2011-11-24Version 3
We define two natural classes of functions, called 2-open and 2-closed, that are closest to open and closed functions. We show that they have the following property: there are $X_i \subset X$ $ (i=1,2,...$) such that $f|X_i$ are open or closed functions onto $f(X_i)$ and $f(X_i)$ cover $Y.$
Comments: 5 pages. arXiv admin note: substantial text overlap with arXiv:1102.3253
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