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math.GN2011
Preservation of the Borel class under open- functions
Alexey Ostrovsky
Let be a Borel subset of the Cantor set \textbf{C} of additive or multiplicative class and be a continuous function with compact preimages of points onto $Y \…
math.GN2011
Countable open and closed functions
Alexey Ostrovsky
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…