  Let $(\mathrm{M}, \omega_{0})$ be a connected paracompact smooth oriented
manifold. We establish a necessary and sufficient conditions on Lie subalgebra
$\mathfrak{a}$ of $\mathrm{T M}$ such that its orbits becomes diffeomorphic to
an open convex set of $\mathbb{R}^{n}$, where $n$ is the orbit dimension.
