\Bibitem{Vah86} \by A.~I.~Vahabov \paper Completeness of the eigenfunctions of irregular differential operators in a space of vector-valued functions \jour Mat. Zametki \yr 1986 \vol 40 \issue 2 \pages 197--202 \mathnet{http://mi.mathnet.ru/mzm5146} \mathscinet{http://mathscinet.ams.org/mathscinet-getitem?mr=864283} \zmath{https://zbmath.org/?q=an:0621.34015} \transl \jour Math. Notes \yr 1986 \vol 40 \issue 2 \pages 611--614 \crossref{https://doi.org/10.1007/BF01159115} \isi{https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=Publons&SrcAuth=Publons_CEL&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=A1986G235400018}