  In the present paper the exhaustive topological classification of nonsingular
Morse-Smale flows of $n$-manifolds with two limit cycles is presented.
Hyperbolicity of periodic orbits implies that among them one is attracting and
another is repelling. Due to Poincare-Hopf theorem Euler characteristic of
closed manifold $M^n$ which admits the considered flows is equal to zero. Only
torus and Klein bottle can be ambient manifolds for such flows in case of
$n=2$. Authors established that there exist exactly two classes of topological
equivalence of such flows of torus and three of the Klein bottle. There are no
constraints for odd-dimensional manifolds which follow from the fact that Euler
characteristic is zero. However, it is known that orientable $3$-manifold
admits a flow of considered class if and only if it is a lens space. In this
paper, it is proved that up to topological equivalence each of $\mathbb S^3$
and $\mathbb RP^3$ admit one such flow and other lens spaces two flows each.
Also, it is shown that the only non-orientable $n$-manifold (for $n>2$), which
admits considered flows is the twisted I-bundle over $(n-1)$-sphere. Moreover,
there are exactly two classes of topological equivalence of such flows. Among
orientable $n$-manifolds only the product of $(n-1)$-sphere and the circle can
be ambient manifold of a considered flow and the flows are split into two
classes of topological equivalence.
