\Bibitem{Kro89} \by V.~G.~Krotov \paper Differential properties on the boundary of functions that are holomorphic in the unit ball in~$C^N$ \jour Mat. Zametki \yr 1989 \vol 45 \issue 2 \pages 51--59 \mathnet{http://mi.mathnet.ru/mzm3450} \mathscinet{http://mathscinet.ams.org/mathscinet-getitem?mr=1002517} \zmath{https://zbmath.org/?q=an:0682.32003|0667.32007} \transl \jour Math. Notes \yr 1989 \vol 45 \issue 2 \pages 122--128 \crossref{https://doi.org/10.1007/BF01158056} \isi{https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=Publons&SrcAuth=Publons_CEL&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=A1989CA56700022}