@article{SM_1991_69_1_a13,
     author = {Ya. L. Umanskii},
     title = {Necessary and sufficient conditions for topological equivalence of three-dimensional {Morse--Smale} dynamical systems with a~finite number of singular trajectories},
     journal = {Sbornik. Mathematics},
     pages = {227--253},
     publisher = {mathdoc},
     volume = {69},
     number = {1},
     year = {1991},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1991_69_1_a13/}
}