2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/145776This article proposes an initiation to Écalle's mould calculus, a powerful combinatorial tool which yields surprisingly explicit formulas for the normalising series attached to an analytic germ of singular vector field. This is illustrated on the case of saddle-node singularities, generated by two-dimensional vector fields which are formally conjugate to Euler's vector field $x^2\frac{\pa}{\pa x}+(x+y)\frac{\pa}{\pa y}$, and for which the formal normalisation proves to be resurgent in $1/x$.13 pages. A paraître dans Rev. Semin. Iberoam. Mat. Singul. TordesillasDynamical Systemstext