\Bibitem{KusKut83} \by A.~G.~Kusraev, S.~S.~Kutateladze \paper Subdifferentials in Boolean-valued models of set theory \jour Sibirsk. Mat. Zh. \yr 1983 \vol 24 \issue 5 \pages 109--122 \mathnet{http://mi.mathnet.ru/smj6768} \mathscinet{http://mathscinet.ams.org/mathscinet-getitem?mr=0723482} \zmath{https://zbmath.org/?q=an:0573.03022} \transl \jour Siberian Math. J. \yr 1983 \vol 24 \issue 5 \pages 735--746 \crossref{https://doi.org/10.1007/BF00969600} \isi{https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=Publons&SrcAuth=Publons_CEL&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:A1983SY70000011}