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On the differences of upper semicontinuous quasi-continuous functions. (English) Zbl 0941.26002
The paper deals with the characterization of the difference of upper semicontinuous quasi-continuous functions by means the extreme limits on the set of continuity points. In detail if $$f_1$$ and $$f_2$$ are upper semicontinuous functions such that $$f_1 - f_2$$ is Darboux and quasi-continuous, then $$f_1 - f_2$$ can be written as a difference of two Darboux upper semicontinuous functions.
##### MSC:
 26A15 Continuity and related questions (modulus of continuity, semicontinuity, discontinuities, etc.) for real functions in one variable 54C08 Weak and generalized continuity
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##### References:
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