\Bibitem{Nik92} \by V.~V.~Nikulin \paper Decay of a vertical tornado-like vortex \jour Prikl. Mekh. Tekh. Fiz. \yr 1992 \vol 33 \issue 4 \pages 42--47 \mathnet{http://mi.mathnet.ru/pmtf4108} \transl \jour J. Appl. Mech. Tech. Phys. \yr 1992 \vol 33 \issue 4 \pages 515--519 \crossref{https://doi.org/10.1007/BF00864274}