\Bibitem{Art79} \by V.~A.~Artamonov \paper Letter to the Editor \jour Russian Math. Surveys \yr 1979 \vol 34 \issue 2 \mathnet{http://mi.mathnet.ru/eng/rm4077} \mathscinet{https://mathscinet.ams.org/mathscinet-getitem?mr=535735} \zmath{https://zbmath.org/?q=an:0404.17002}