Conjugate functions and the restricted Denjoy integral

We study the functions conjugate to Denjoy integrable functions. In particular, it is shown that if $f$ and its conjugate $\overline f$ are integrable in the restricted Denjoy sense then the conjugate series coincides with the Fourier–Denjoy series of the conjugate function, $(D^*)\sigma[\overline f]=(D^*)\overline\sigma [f]$, and the Riesz equation $(D^*)\int_0^{2\pi}\varphi\overline f\,dx=-(D^*)\int_0^{2\pi}f\overline\varphi\,dx$ holds provided that $\varphi$ and its conjugate function $\overline\varphi$ are of bounded variation.
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