\Bibitem{Bai81} \by S.~P.~Baiborodov \paper Approximation of functions of several variables by de la Vall\'ee Poussin rectangular sums \jour Mat. Zametki \yr 1981 \vol 29 \issue 5 \pages 711--730 \mathnet{http://mi.mathnet.ru/mzm6260} \mathscinet{http://mathscinet.ams.org/mathscinet-getitem?mr=621296} \zmath{https://zbmath.org/?q=an:0491.42002} \transl \jour Math. Notes \yr 1981 \vol 29 \issue 5 \pages 362--372 \crossref{https://doi.org/10.1007/BF01158360} \isi{https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=Publons&SrcAuth=Publons_CEL&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=A1981ND21900006}