\Bibitem{Kov49} \by P.~I.~Koval' \paper On Stieltjes integrals \jour Russian Math. Surveys \yr 1949 \vol 4 \issue 6 \mathnet{http://mi.mathnet.ru//eng/rm8674} \mathscinet{http://mathscinet.ams.org/mathscinet-getitem?mr=33338} \zmath{https://zbmath.org/?q=an:0035.32801}