“…x ∈ R n , with f (x) = O * ( x 2 ) ∈ C ω (R n , 0), the study of the theory of local integrability or of the existence of first integrals at the origin can be traced back to Poincaré [16]. Since then, the theory of local integrability has been greatly developed, see for example [1,2,4,5,6,8,15,17,18,19,20,21,22]. Hereafter, O * ( x 2 ) denotes a function (or a vector-valued function) without constant and linear terms in its Taylor expansion, and C ω (R n , 0) denotes the set of analytic functions defined in a neighborhood of the origin.…”