\Bibitem{Bar46} \by E.~Barbashin \paper On $\sigma$-coverings of spaces \jour Sb. Math. \yr 1946 \vol 60 \issue 3 \mathnet{http://mi.mathnet.ru/eng/sm6286} \mathscinet{https://mathscinet.ams.org/mathscinet-getitem?mr=16651} \zmath{https://zbmath.org/?q=an:0061.40006}