Abstract:
It is proved that the following conditions are equivalent: the function $\varphi[a,b]\to R$ is absolutely upper semicontinuous (see [1]); $\varphi$ is a function of bounded variation with decreasing singular part; there exists a summable function $g:[a,b]\to R$ such that for any $t'\in[a,b]$ and $t''\in[t',b]$, we have $\varphi(t'')-\varphi(t')\le\int_{t'}^{t''}g(s)\,ds$.
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