\Bibitem{And56} \by V.~A.~Andrunakievich \paper Biregular rings \jour Sb. Math. \yr 1956 \vol 81 \issue 4 \mathnet{http://mi.mathnet.ru//eng/sm5147} \mathscinet{http://mathscinet.ams.org/mathscinet-getitem?mr=86796} \zmath{https://zbmath.org/?q=an:0071.02903}