\Bibitem{GalPocShu24} \by V.~D.~Galkin, O.~V.~Pochinka, D.~D.~Shubin \paper Classification of non-singular four-dimensional flows with a non-twisted saddle orbit \jour Sb. Math. \yr 2024 \vol 215 \issue 11 \mathnet{http://mi.mathnet.ru//eng/sm10091}