\Bibitem{GorZak11} \by V.~Goryunov, V.~Zakalyukin \paper Vladimir I. Arnold \jour Mosc. Math.~J. \yr 2011 \vol 11 \issue 3 \pages 409--411 \mathnet{http://mi.mathnet.ru/mmj443} \mathscinet{https://mathscinet.ams.org/mathscinet-getitem?mr=2894422}