\Bibitem{Gal90} \by \`E.~M.~Galeev \paper Approximation of classes of periodic functions of several variables by nuclear operators \jour Mat. Zametki \yr 1990 \vol 47 \issue 3 \pages 32--41 \mathnet{http://mi.mathnet.ru/mzm3192} \mathscinet{http://mathscinet.ams.org/mathscinet-getitem?mr=1052065} \zmath{https://zbmath.org/?q=an:0723.41018} \transl \jour Math. Notes \yr 1990 \vol 47 \issue 3 \pages 248--254 \crossref{https://doi.org/10.1007/BF01138503} \isi{https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=Publons&SrcAuth=Publons_CEL&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=A1990EL38300005}