\Bibitem{Kub57} \by A.~A.~Kubenskii \paper Functional-closed spaces \jour Dokl. Akad. Nauk SSSR \yr 1957 \vol 117 \issue 5 \pages 748--750 \mathnet{http://mi.mathnet.ru/dan22574} \mathscinet{http://mathscinet.ams.org/mathscinet-getitem?mr=0091447} \zmath{https://zbmath.org/?q=an:0113.37603}