\Bibitem{Gui66}
\by A.~Guichardet
\paper A letter to the editors
\jour Dokl. Akad. Nauk SSSR
\yr 1966
\vol 168
\issue 6
\pages 1231
\mathnet{http://mi.mathnet.ru/dan32360}
\mathscinet{https://mathscinet.ams.org/mathscinet-getitem?mr=0196511}
\zmath{https://zbmath.org/?q=an:0178.49204}