It is well known that there is no general method to solve differential equations even in the case of the simplest manifold, namely the real line ℝ. Failing that, mathematicians rather try to study the geometrical and topological properties of integral manifolds and their asymptotic behavior. This is exactly the purpose of
: the qualitative study of differential equations. It was initiated by the works of H. Poincaré and I. Bendixson, and developed later by C.