\Bibitem{Kag63} \by A.~M.~Kagan \paper On Robbins's scheme \jour Dokl. Akad. Nauk SSSR \yr 1963 \vol 150 \issue 4 \pages 733--735 \mathnet{http://mi.mathnet.ru/dan28125} \mathscinet{http://mathscinet.ams.org/mathscinet-getitem?mr=0152051} \zmath{https://zbmath.org/?q=an:0136.39803}