\Bibitem{ZelSmo91} \by M.~B.~Zel'man, B.~V.~Smorodskii \paper Linear evolution of perturbations in boundary layers with a velocity profile inflection \jour Prikl. Mekh. Tekh. Fiz. \yr 1991 \vol 32 \issue 1 \pages 50--55 \mathnet{http://mi.mathnet.ru/pmtf4190} \transl \jour J. Appl. Mech. Tech. Phys. \yr 1991 \vol 32 \issue 1 \pages 46--51 \crossref{https://doi.org/10.1007/BF00852262}